Particulate materials

ABSTRACT

The present invention relates to active substances in particulate form, to methods for preparing them and to their uses. The present invention provides particulate powders, such as might be of use for delivery using a dry powder inhaler (DPI) or similar delivery device, having properties which may be beneficial to the DPI delivery process.

FIELD OF THE INVENTION

[0001] The present invention relates to active substances in particulateform, to methods for preparing them and to their uses.

BACKGROUND OF THE INVENTION

[0002] Certain pharmaceuticals may be delivered to the nose and/or lungsof a patient by inhalation, using an inhaler device of which there areseveral known types. Pulmonary delivery by aerosol inhalation hasreceived much attention as an attractive alternative to intravenous,intramuscular, and subcutaneous injection, since this approacheliminates the necessity for injection syringes and needles. Pulmonarydelivery also limits irritation to the skin and body mucosa which arecommon side effects of transdermally, iontophoretically and intranasallydelivered drugs, eliminates the need for nasal and skin penetrationenhancers (typical components of intranasal and transdermal systemsoften cause skin irritation/dermatitis), is economically attractive, isamenable to patient self-administration and is often preferred bypatients over alternative modes of administration.

[0003] Of particular interest in the context of the present inventionare pulmonary delivery techniques which rely on the inhalation of apharmaceutical formulation by a patient so that the active drug withinthe dispersion can reach the distal (alveolar) regions of the lung.

[0004] A variety of aerosolization systems have been proposed todisperse pharmaceutical formulations. For example, U.S. Pat. Nos.5,785,049 and 5,740,794, the disclosures of which are hereinincorporated by reference, describe exemplary active powder dispersiondevices which utilize a compressed gas to aerosolize a powder. Othertypes of aerosolization systems include metered dose inhalers (MDIs),which typically have a drug that is stored in a propellant, andnebulizers (which aerosolize liquids using a compressed gas, usuallyair).

[0005] An alternative type of inhaler is known as a dry powder inhaler(DPI) and delivers the drug (or a composition containing the drug, forinstance together with a pharmaceutically acceptable excipient) in theform of a dry air-borne particulate powder. DPIs include single useinhalers such as those disclosed in U.S. Pat. Nos. 4,069,819, 4,995,385,3,991,761 and 6,230,707, and in WO-99/45986, WO-99/45987, WO-97/27892and GB-1 122 284; multi-single dose inhalers such as those disclosed inU.S. Pat. Nos. 6,032,666 and 5,873,360 and in WO-97/25086; andmulti-dose inhalers containing powder in a bulk powder reservoir such asthose disclosed in U.S. Pat. No. 4,524,769.

[0006] Particulate active substances, such as drugs, may be produced bya variety of known methods, including for example crystallisation fromsolution, anti-solvent precipitation from solution, milling,micronisation, spray drying, freeze drying or combinations of suchprocesses. Also known are particle formation processes which make use ofsupercritical or near-critical fluids, either as solvents for thesubstance of interest—as in the process known as RESS (Rapid Expansionof Supercritical Solution—see Tom & Debenedetti, J. Aerosol. Sci., 22(5), 555-584 (1991))—or as anti-solvents to cause the substance toprecipitate from another solution—as in the process known as GAS (GasAnti-Solvent) precipitation—see Gallagher et al, ACS Symp. Ser., 406,p334 (1989).

[0007] In general, however, known processes for producing inhalabledrugs can often yield particles which give less than satisfactoryperformance in DPI and similar delivery devices. For example, thedispersion of many prior art dry powder formulations from inhalationdevices exhibits a flow rate dependence such that dispersion of thepowder from the device increases with the patient's inspiratory effort.Alternatively, many formulations require mixing or blending with largercarrier particles such as lactose in order to deliver the particleseffectively to the deep lung.

[0008] It would therefore be desirable to provide particulate drugs, andindeed other active substances which may need to be delivered as dry(ie, without a fluid carrier) powders using a DPI or analogousmechanism, which can demonstrate improved performance in such a context,in particular improved dispersibility and aerosol performance in fluidsand especially in gases such as air.

SUMMARY OF THE INVENTION

[0009] The present invention provides particulate powders, such as mightbe of use for delivery using a DPI or similar delivery device, havingproperties which may be beneficial to the DPI delivery process. Theseproperties are illustrated in the examples below.

[0010] In particular, according to a first aspect, the present inventioncan provide an active substance in particulate form, preferably preparedusing a SEDS™ particle formation process as defined below, whichexhibits one or more (preferably two or more, more preferably at leastthree) of the following characteristics:

[0011] a) the particles have a low surface energy. In particular, theypreferably exhibit a low value for the surface energy related parameterγ_(S) ^(D) (the dispersive component of surface free energy, as definedin the examples below, which reflects non-polar surface interactions)and/or for the parameter ΔG_(A) (the specific component of surface freeenergy of adsorption, again as defined in the examples, which reflectspolar surface interactions), for instance when compared to particles ofthe same active substance prepared using a non-SEDS™ particle formationprocess and preferably having the same or a smaller volume meandiameter. In the case of the parameter ΔG_(A), the value for the activesubstance of the present invention, for any given polar solvent, ispreferably lower by a factor of at least 1.2, preferably at least 1.4 or1.5, than that for the corresponding non-SEDS™-produced substance.

[0012] b) the particles exhibit a low surface adhesion and/orcohesiveness (which may be related to their surface energy). Inparticular, they may exhibit lower adhesiveness than those of the sameactive substance produced by a non-SEDS™ particle formation process.

[0013] c) the particles show little or no tendency for aggregation(again this may be related to their surface properties such as surfaceenergy and adhesiveness), or at least form less stable aggregates thanthose of the same active substance produced by a non-SEDS™ particleformation process.

[0014] d) the particles have a volume mean aerodynamic diameter of 7 μmor less, preferably 5 μm or less, more preferably 4 μm or 3 μm or less,such as from 1 to 5 μm, from 1 to 4 μm or from 1 to 2 μm.

[0015] e) the particles have a volume mean geometric diameter of 5 μm orless, preferably 4 μm or less, more preferably from 1 to 5 μm, mostpreferably from 1 to 4 or from 2 to 4 μm.

[0016] f) the particles have a particle size distribution (x₉₀) of 10 μmor less, preferably also a value for (x₉₈) of 10 μm or less, preferablyalso a value for (x₉₉) of 10 μm or less. Typically each of these valueswill be from 0.5 to 10 μm.

[0017] g) when measured using a cascade impactor technique (at lowturbulence), the particles have a particle size spread, defined as(x₉₀−x₁₀)/x₅₀, of 1.3 or less, preferably of 1.25 or 1.2 or less, volumemean diameter of 6 μm or less, preferably of 5.5 μm or less, morepreferably of 5.2 μm or less. Their particle size spread under theseconditions is preferably at least 5%, more preferably at least 10%,still more preferably at least 12%, smaller than that of the same activesubstance produced by a non-SEDS™ particle formation process, and theirvolume mean diameter preferably at least 10%, more preferably at least15%, still more preferably at least 20%, smaller than that of thenon-SEDS™ substance.

[0018] h) the particles are crystalline, or substantially so, and inparticular are more crystalline than those of the same active substanceproduced by a non-SEDS™ particle formation process. Their X-raydiffraction patterns thus preferably exhibit reduced diffraction linebroadening and/or a higher signal-to-noise ratio than the X-raydiffraction patterns for the same active substance produced by anon-SEDS™ process. The crystalline particles may exhibit reduced crystallattice imperfections such as strain defects (point defects and/ordislocations) and/or size effects (grains, small-angle boundaries and/orstacking faults), as compared to crystals of the same active substanceproduced by a non-SEDS™ process—such imperfections tend to be associatedwith increased line broadening in the X-ray diffraction patterns. Inparticular, the particles may exhibit a lower crystal strain, and/or ahigher crystal domain size, than crystals of the same active substanceproduced by a non-SEDS™ particle formation process.

[0019] i) where the active substance is capable of existing in two ormore different polymorphic forms, the particles consist of only one suchform, with a purity of 99.5% w/w or greater, preferably of 99.8% w/w orgreater, with respect to the other polymorphic forms. More preferably,the active substance has a higher activation energy for conversion toone or more other polymorphic forms than does a sample of the sameactive substance prepared using a non-SEDS™ particle formation process.

[0020] j) the particles have a lower surface charge (for instance, meanspecific charge) than those of the same active substance produced by anon-SEDS™ particle formation process.

[0021] k) the particles exhibit superior powder flow properties (whichmay be related to lower surface charge and/or adhesiveness) as comparedto those of the same active substance produced by a non-SEDS™ particleformation process; for instance, they may be more free-flowing and/orthey may deaggregate more efficiently when dispersed in a fluid such asin a DPI device, particularly at low turbulence and/or shear stresslevels.

[0022] l) the particles have a bulk powder density which is lower thanthat of the same active substance produced by a non-SEDS™ particleformation process. They preferably have a bulk powder density of lessthan 0.5 g/cm³, more preferably of 0.4 g/cm³ or less, most preferably of0.2 g/cm³ or less.

[0023] m) the particles have a specific surface area which is higherthan that of the same active substance produced by a non-SEDS™ particleformation process.

[0024] n) the “shape factor” of the particles, by which is meant theratio of (a) their measured specific surface area (ie, surface area perunit volume) to (b) their theoretical specific surface area ascalculated from their measured diameters assuming spherical particles,is higher than that of the same active substance produced by a non-SEDS™particle formation process. Preferably this shape factor is at least 2,more preferably at least 3, most preferably at least 3.5.

[0025] o) the “shape coefficient”, α_(S,V) of the particles, determinedfrom image (eg, SEM) analysis and as defined in the following equation:

α_(S,V)≅6d _(s) ³ /d _(v) ³

[0026] where the mean projected diameter, d_(s), is given by:

d _(s)=(4S/π)^(1/2)=((2/π)(ab+bc+ca))^(1/2) and

[0027] the volume particle diameter, d_(v), is given by

d _(v)=(6V/π)^(1/3)=(6abc/π)^(1/3)

[0028] is higher than that of the same active substance produced by anon-SEDS™ particle formation process, preferably at least 1.5 times asgreat, more preferably at least twice as great. Preferably this shapecoefficient is at least 10, more preferably at least 15, most preferablyat least 18 or at least 20. It may alternatively be calculated fromspecific surface area measurements, laser diffraction particle sizemeasurements and the theoretical crystal density, as defined in thefollowing equation:

S _(v)=α_(S,V)/ρ_(xmin)∫^(xmax) x ⁻¹ q ₃(x)dx

[0029] p) the “aerodynamic shape factor” of the particles, χ, is greaterthan that for the same active substance produced by a non-SEDS™ particleformation process, preferably at least 20% greater, more preferably atleast 30% or at least 40% greater. χ is the ratio of the drag force on aparticle to the drag force on the particle volume-equivalent sphere atthe same velocity, and may be calculated as described in the followingequation:

χ≅((C _(d)(d _(S))C _(c)(d _(V)))/(C _(d)(d _(V))C _(c)(d _(S))))(d _(S)/d _(V))²

[0030] For a product according to the invention it may be 1.4 orgreater, preferably 1.5 or greater, most preferably 1.7 or 1.8 orgreater.

[0031] q) the particles have reduced surface roughness compared to thoseof the same active substance produced by a non-SEDS™ particle formationprocess.

[0032] By “non-SEDS™ particle formation process” is meant a particleformation process other than the SEDS™ process defined below, forexample one involving micronisation, granulation and/or solventcrystallisation under sub-critical conditions, and in particular oneinvolving micronisation. In general, comparisons between substancesaccording to the invention and those made by non-SEDS™ techniques aresuitably made using in each case particles of the same or a comparablesize (eg, no more than 30% or even than 20% different in size) and/orshape.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 depicts the percentage dissolution against time forparticles processed according to the invention compared to micronised.

[0034]FIG. 2 depicts an AFM analysis of material process according tothis invention.

[0035]FIG. 3 is a graph showing RMS surface roughness data for materialsprocessed according to the invention.

[0036]FIG. 4 is a schematic of the SEDS process.

[0037]FIGS. 5a-f are SEMs of particles produces according to theinvention.

[0038]FIGS. 6a-c depict X-ray powder patterns illustrating thecrystallinity of micronised and samples produced according to theinvention.

[0039]FIG. 7 depicts the heat flow (μW) for both micronised and SEDS™powders of terbutaline sulphate.

[0040]FIG. 8 depicts the strange attractor plots for terbutalinesupphate analysed at high (100 seconds per revolution) rotation speed.

[0041]FIG. 9 depicts the strange attractor plots for TBS analysed atmedium (145 seconds per revolution) rotation speed.

[0042]FIGS. 10 and 11 compare the in vitro performance of micronised andSEDS™ processed terbutaline sulphate analysed in a lactose blend as wellas pure drug alone.

DETAILED DESCRIPTION OF THE INVENTION

[0043] It has been found that particulate active substances having oneor more of the above properties tend to exhibit improved performance, inparticular good dispersibility, in delivery devices such as inhalers,especially dry powder inhalers and more especially passive dry powderinhalers. In particular a correlation has been found between lowerparticle surface energy and improved DPI performance. Similarly, lowerstrain, higher crystallinity and higher polymorphic purity have beenassociated with reduced agglomeration and particle adhesion, and withlower electrostatic charge, again properties which lead to improved DPIperformance. Higher specific surface areas, and higher shape factors,have also been found to accompany improved DPI performance. For a givenparticle size, products according to the invention can demonstratesignificantly better performance in passive dry powder inhalers thanproducts made by conventional techniques such as spray drying, freezedrying, granulation and in particular micronisation.

[0044] Thus, the active substance of the invention, when used in apassive dry powder inhaler or analogous delivery device (for example thecommercially available Clickhaler™), preferably yields a fine particlefraction in the emitted dose of 20% or greater, preferably 26% orgreater, more preferably 31% or greater, in cases 35% or 40% or 50% oreven 55% or greater. Instead or in addition, its fine particle fractionmay be at least 20% greater, preferably at least 25% or 30% or 40% or50% or 60% or 80% or 100% greater, more preferably at least 110% or 120%or 130% or 140% greater, than that of the same active substance producedby a non-SEDS™ particle formation process and having the same or asmaller volume mean diameter.

[0045] The active substance is preferably in a substantially (eg, 95%w/w, preferably 98% or 99% w/w or greater) pure form. It preferablycontains low levels of residual solvent, for example less than 500 ppm,more preferably less than 200 ppm, most preferably less than 150 or 100ppm residual solvent, by which is meant solvent(s) which were present atthe point of particle formation. Still more preferably the substancecontains no detectable residual solvent, or at least only levels belowthe relevant quantification limit(s). In particular residual solventlevels in the bulk particles, as opposed to merely at their surfaces,are likely to be lower than in particles of the same active substanceproduced by a non-SEDS™ process.

[0046] In cases, the fine particle fraction yielded by an activesubstance according to the invention, for instance in an Andersen™cascade impactor, may be up to 150% or 175% or even 200% or 250% or 280%of that of the same active substance produced by a non-SEDS™ process.Such improvements may often be exhibited even if the particle size ofthe substance of the invention is significantly greater (eg, at least30% or 50% or 75% or 90% greater) than that of the non-SEDS™-producedsubstance. They can also be exhibited in the absence of dispersionenhancing additives such as surfactants, in the absence ofexcipient/carrier materials and/or in unimodal (with respect to particlesize) systems.

[0047] Particular improvements (with respect to substances made bynon-SEDS™ processes) may be seen where the active substance is usedalone as opposed to in a blend with an excipient such as lactose.

[0048] The total emitted dose for a substance according to the inventionmay also, in this context, be at least 10% greater, preferably at least15% greater, more preferably at least 20% or 25% or 30% greater, thanthat for the same active substance made by a non-SEDS™ process, eitherwith or without excipient(s). Generally the substances of the inventionmay deposit on the impactor stages with a narrower distribution(typically weighted more to the lower stages such as 1 to 3) than forthose made by non-SEDS™ processes.

[0049] At relatively low dispersing pressures, for instance 2 bar orless, an active substance according to the invention has been foundcapable of yielding a significantly higher proportion of primaryparticles in the respirable size range than the same active substanceproduced by a non-SEDS™ process, the latter often tending to form stable(ie, not dispersible at these pressures) agglomerates above thepreferred 5 μm limit. This again indicates reduced particle cohesivenessand/or reduced inter-particulate contact area in an active substanceaccording to the invention. The volume mean particle diameter d_(4,3) ofthe particles of the invention (calculated from cascade impactor data)may thus appear larger than that for non-SEDS™-produced particles whendispersed at pressures of 2 bar and above, but smaller at pressuresbelow 2 bar, for instance 1.8 bar or below, where the dispersion (ordeaggregation) ability of the particles plays a more dominant role.

[0050] Since the viscous shear stress within the impactor will affectthe dispersion behaviour of the particles and hence their apparentvolume mean diameter, particles according to the invention exhibitvolume mean diameters lower than those of their non-SEDS™ equivalents atlower viscous shear stresses, for instance below 20 Nm⁻² or even up to30 or 40 Nm⁻².

[0051] At such low shear stress levels, particles according to theinvention appear to undergo significantly less aggregation, or to formsignificantly less stable aggregates, than those produced by a non-SEDS™process which may produce stable aggregates well outside the 5 μmrespirable limit. The particles of the invention, at these shear stresslevels (or at least at shear stress levels between 5 and 30 Nm⁻² orbetween 10 and 30 Nm⁻²) can produce a large fraction of primaryparticles in the respiratory size range, preferably having a volume meandiameter of less than 6 or more preferably less than 5 μm.

[0052] Thus, the volume mean particle diameter of an active substanceaccording to the invention, derived from cascade impactor data in themanner defined in the Examples below, may be at least 10% smaller,preferably at least 15% or at least 20% smaller, than that of the sameactive substance produced by a non-SEDS™ particle formation technique,even where its volume mean diameter measured at higher dispersions usinganother technique such as laser diffraction or time-of-flight is greaterthan (for instance, up to 30% or 50% or even 100% greater than) that ofthe non-SEDS™ substance. This indicates that for a given size, particlesaccording to the invention can give superior performance onaerosolisation.

[0053] Accordingly, particulate active substances of the presentinvention may be particularly advantageous for use with passive drypowder inhalers which operate in the lower region of turbulent stresseswhen dispersing the powder they contain.

[0054] In the context of the present invention, a passive dry powderinhaler is a device for use in delivering a powdered active substance toa patient, in which the patient's inspiratory effort is used as the solepowder dispersing means. In other words, the powder is not delivered ina pressurised fluid as in many metered dose inhalers, and nor does itsdelivery require the use of a rotating impeller or other mechanicalmeans.

[0055] A second aspect of the present invention provides a method forselecting a particulate active substance for use in a dry powderinhaler, in particular a passive dry powder inhaler, which methodinvolves the assessment of, and selection on the basis of, one or more(preferably two or more, more preferably three or more) of the abovedescribed properties of active substances according to the first aspectof the invention.

[0056] A third aspect provides the use of an active substance accordingto the first aspect, in a dry powder inhaler and in particular in apassive dry powder inhaler, for the purpose of achieving improved activesubstance delivery. Improved delivery in this context may involveimproved powder dispersion, more accurate dosage delivery, moreconsistent dosage delivery and/or a higher fine particle fraction in theemitted dose, in particular at relatively low dispersing pressures suchas 2 bar or less or 1.8 bar or less.

[0057] Particle surface energies may be measured using inverse gaschromatography (IGC), for instance using a gas chromatograph from theHewlett Packard™ series. Surface energy measurements ideally takeaccount of the dispersive component of the surface free energy, γ_(S)^(D), the specific component of the surface free energy of adsorption,ΔG_(A), the acid-base parameters and/or the total (Hildebrand)solubility parameter, which takes into account dispersive, polar andhydrogen-bonding interactions on particle surfaces and thus reflects theinter-particle adhesion. The dispersive component γ_(S) ^(D) may beassessed using non-polar probes such as alkanes, and the specificcomponent ΔG_(A) may be assessed using data from both polar andnon-polar probes, the former having both dispersive and specificcomponents of surface free energy of adsorption.

[0058] Thus, gas chromatography measurements suitably involve the use ofboth non-polar and polar probes, examples of the former being alkanessuch as pentane, hexane, heptane, octane and nonane and of the latterbeing diethyl ether, toluene, acetone, ethyl acetate, chloroform,dioxane, dichloromethane and tetrahydrofuran.

[0059] In the case of the dispersive component γ_(S) ^(D), the value forthe active substance of the present invention is preferably at least 5%lower, more preferably at least 10% lower, most preferably at least 12%or 15% or 20% or 30% lower, than that for the same active substance madeby a non-SEDS™ particle formation process.

[0060] In the case of the specific component ΔG_(A), the value for theactive substance of the present invention is preferably at least 10%lower, more preferably at least 15% lower, most preferably at least 20%or 30% or 50% or 80% lower, than that for the same active substance madeby a non-SEDS™ particle formation process.

[0061] In the case of the Hildebrand solubility parameter δ, the valuefor the active substance of the present invention is preferably at least5% lower, more preferably at least 8% lower, most preferably at least10% lower, than that for the same active substance made by a non-SEDS™particle formation process.

[0062] Overall, particulate active substances according to the presentinvention tend to have lower surface activity (for example with respectto solvent adsorption) and greater surface stability than those producedby non-SEDS™ particle formation processes, with a more ordered surfacestructure. Their lower surface energy may be manifested by a lower valuefor K_(A) and/or K_(D), for instance as measured in Example 2,indicative of weaker acidic and/or basic interactions respectively atthe particle surfaces. For instance, their K_(A) may be at least 5%,preferably at least 10% or at least 12%, lower than that of the sameactive substance made by a non-SEDS™ particle formation process, and/ortheir K_(D) may be at least 30%, preferably at least 50% or at least 60%lower.

[0063] The specific surface energy E_(S) of a particulate activesubstance according to the invention, calculated as per the followingequation:

E _(s)=0.683(δ²/α_(S,V) ^(2/3))Ω^(1/3)

[0064] where δ is the Hildebrand solubility parameter, α_(S,V) is theshape coefficient, and Ω is the molecular volume

[0065] is preferably at least 10%, more preferably at least 20%, stillmore preferably at least 30% or 40%, lower than that of the same activesubstance produced by a non-SEDS™ particle formation process, and mighttypically be 100 mJ/m² or lower, more preferably 90 or 80 or 70 mJ/m² orlower.

[0066] A lower aggregation tendency in particles according to theinvention may be reflected in a lower theoretical aggregate tensilestrength σ, which may be calculated as described in the followingequation:

σ≅15.6(ρ_(B)/ρ_(C))⁴ W/d _(s)

[0067] where ρ_(B) and ρ_(C) are the bulk density and particle crystaldensity, respectively, and W is the work of adhesion. Preferably theratio of a for particles of the invention to that for particles of thesame active substance produced by a non-SEDS™ process is 0.8 or lower,more preferably 0.5 or lower, most preferably 0.3 or 0.2 or 0.1 orlower, especially when polar interactions are taken into account.

[0068] Similarly, the aerodynamic stress required to disperse aggregatesof particles according to the invention (for instance, calculated fromcascade impactor measurements, as described in the Examples below) istypically lower than that required to disperse aggregates of the sameactive substance prepared by a non-SEDS™ particle formation process.Ideally the ratio of the two stresses (SEDS™ product: non-SEDS™ product)is 0.8 or lower, more preferably 0.5 or lower, most preferably 0.3 or0.2 or lower. Inter-particle aggregation can be particularly relevant toDPI performance since such aggregates tend to survive the pre-separationstage. Aggregation tendencies can also be relevant when an activesubstance is blended with a carrier such as lactose, where dispersionmay depend on the break-up of active-carrier aggregates—again,typically, substances according to the invention may tend to form lessstable aggregates with carrier particles.

[0069] Particle sizes may be measured for instance using (a) anAeroSizer™ time-of-flight instrument (which gives a mass meanaerodynamic equivalent particle diameter, MMAD, measured at Reynoldsnumbers greater than 1) or (b) a laser diffraction sensor such as theHelos™ system (which provides a geometric projection equivalent massmedian diameter). Volume mean aerodynamic and geometric diametersrespectively may be obtained from these measurements using commerciallyavailable software packages.

[0070] The aerodynamic diameter d_(A) of a particulate active substanceaccording to the invention, measured according to the examples below, ispreferably 2 μm or below, more preferably 1.8 μm or below, mostpreferably 1.6 μm or below.

[0071] Particle size distributions may be measured using laserdiffraction and/or time-of-flight measurements, for instance using anAeroSizer™ time-of-flight instrument equipped with an AeroDisperser™(TSI Inc, Minneapolis, USA) and/or a Helos™ laser diffraction sensorwith Rodos™ dry powder air dispersion system (Sympatec GmbH, Germany).Volume particle size distributions based on aerodynamic equivalentparticle diameters are preferred. Ideally time-of-flight measurementsare gathered at high shear forces, high deaggregation levels and/or lowfeed rates, in order to facilitate production of primary aerosolparticles.

[0072] Particle size distribution (PSD) data, in particular obtained bylaser diffraction measurements, may also be used to calculate the shapecoefficient α_(S,V) of particles in the manner described above.

[0073] An active substance according to the invention will suitably havea cumulative particle size distribution such that more than 98% of theparticles are within the respirable particle size range from 0.5 to 10μm.

[0074] Scanning electron microscopy (SEM) may also be used to measurecharacteristic particle dimensions and thus characteristics such asparticle aspect ratios and shape factors.

[0075] Crystallinity of a particulate material may be determined usingX-ray powder diffraction, preferably high resolution X-ray powderdiffraction such as using a synchrotron radiation source. Usingcommercially available software, X-ray diffraction data may be employedto assess the distribution of crystalline domain sizes and the degree ofstrain in the crystals.

[0076] X-ray diffraction line broadening can provide an indication ofcrystal lattice imperfections such as strain defects (point defects ordislocations) and size effects (grains, small-angle boundaries orstacking faults). Line broadening may be manifested for instance by anincreased peak width (eg, full width at half maximum height, FWHM)and/or an increased integral breadth β* (the width of rectangle havingthe same area A and height I as the observed line profile, ie, β*=A/I),for one or more of the diffraction peaks.

[0077] Preferably, for at least one peak in its X-ray diffractionpattern (ideally for two or more, even three or more, peaks), the activesubstance of the invention exhibits a FWHM which is at least 20% lower,more preferably at least 25% lower, most preferably at least 30% or 40%or 50% lower, than that of the corresponding peak (ie, the peak for thesame crystal plane) in the X-ray diffraction pattern of the samesubstance produced by a non-SEDS™ particle formation process. The FWHMof at least one, ideally of at least two or three or even of all, peaksis preferably 0.1° or less, more preferably 0.09° or less, mostpreferably 0.08° or less.

[0078] For at least one peak in its X-ray diffraction pattern (ideallyfor two or more, even three or more, peaks), the active substance of theinvention preferably exhibits an integral breadth β* which is at least20% lower, more preferably at least 25% lower, most preferably at least30% or 40% or 45% lower, than that of the corresponding peak in theX-ray diffraction pattern of the same substance produced by a non-SEDS™particle formation process. The integral breadth of at least one,ideally of at least two or three or even of all, peaks is preferably0.11° or less, more preferably 0.1° or less.

[0079] A reduced level of crystal lattice imperfections, in aparticulate product according to the invention, may also be manifestedby a shift in position, towards higher 2θ values (typically a shift of0.0005° or more, such as of from 0.0005 to 0.005 or from 0.001 to0.0030°, of one or more of the diffraction peaks. This may be associatedwith a decrease in crystal d-spacing (Δd/d) of 0.5% or more, typically1% or more, such as from 1 to 2%, in the product of the invention, andwith a corresponding reduction in crystal volume, ΔV/V, of 0.5% or more,typically 1% or more, such as from 1 to 2%.

[0080] Levels of crystal lattice imperfections may also be assessed withreference to the crystal domain sizes and/or the crystal strain. Domainsizes are typically significantly greater for products according to theinvention, compared to the same active substance produced using anon-SEDS™ particle formation process, and crystal strain is typicallysignificantly lower. Such parameters may be calculated from X-raydiffraction patterns, for instance by analysing the diffraction peakprofiles as a convolution of Cauchy and Gauss integral breadthscontaining size and strain (distortion) contributions, as known in theart. This allows calculation of for example surface-weighted (D_(S))and/or volume weighted (D_(V)) domain sizes, and of a mean-square(Gaussian) strain, ε, which is the total strain averaged over infinitedistance.

[0081] Preferably, the active substance of the invention exhibits asurface-weighted domain size D_(S) which is at least 15% higher, morepreferably at least 20% higher, most preferably at least 30% or 35%higher, than that of the same substance produced by a non-SEDS™ particleformation process. It preferably exhibits a volume-weighted domain sizeD_(V) which is at least 10% higher, more preferably at least 15% higher,most preferably at least 20% or 25% higher, than that of the samesubstance produced by a non-SEDS™ particle formation process. D_(S) mayfor example be 400 Å or greater, and D_(V) may be 700 Å or greater, inan active substance according to the invention.

[0082] Preferably the active substance of the invention exhibits a totalstrain ε which is at least 30% lower, more preferably at least 35%lower, most preferably at least 40% or 45% lower, than that of the samesubstance produced by a non-SEDS™ particle formation process. Its totalstrain may for instance be 0.7×10⁻³ or lower, preferably 0.6×10⁻³ orlower, most preferably 0.5×10⁻³ or lower.

[0083] Domain size and strain may alternatively be calculated from theX-ray diffraction data by Le Bail diffraction profile fitting. Usingsuch computational methods, an active substance according to theinvention preferably exhibits a volume-weighted domain size which is atleast 50% higher, more preferably at least 80% higher, most preferablyat least 90% higher, than that of the same substance produced by anon-SEDS™ particle formation process. It preferably exhibits a strainwhich is at least 40% lower, more preferably at least 50% lower, mostpreferably at least 60% lower, than that of the same substance producedby a non-SEDS™ particle formation process.

[0084] An active substance according to the invention may have anamorphous content of less than 5% w/w, preferably less than 2% w/w, morepreferably less than 1 or even than 0.5 or 0.2% w/w. Ideally itsamorphous phase content is at least 10 times, preferably at least 20 oreven 40 or 50 times, lower than that of the same active substanceproduced by a non-SEDS™ particle formation process.

[0085] A higher bulk crystallinity, in an active substance according tothe invention, may be manifested by a lower moisture uptake at any giventemperature and humidity, and/or by a thermal activity profile with noexothermic or endothermic peaks, for instance as measured in theexamples below.

[0086] Polymorphic purity may be assessed for instance using meltingpoint data (eg, differential scanning calorimetry) or more preferablyusing X-ray powder diffraction (for instance the small-angle X-rayscattering (SAXS) technique) to detect polymorphic transitions duringheating, based on the diffraction peaks characteristic of thepolymorphs.

[0087] An active substance according to the invention is preferably morestable, with respect to polymorphic transitions, than a sample of thesame active substance prepared using a non-SEDS™ particle formationprocess; it will thus typically have a higher activation energy forconversion to one or more other polymorphic forms than will thenon-SEDS™ sample for the same polymorphic transition. More preferably,when heated at a rate of 10° C. per minute or greater at atmosphericpressure, the active substance of the invention will not alter itspolymorphic form. Instead or in addition, the time required forformation of one or more other polymorphs of the active substance,calculated for instance from X-ray diffraction and thermal analysisdata, is preferably 80 seconds or greater, more preferably 90 seconds orgreater. The active substance preferably contains no detectable seednuclei of polymorphic forms other than that desired to be present.

[0088] Enhanced crystallinity and/or polymorphic purity in activesubstances according to the invention are believed to contribute to anoverall higher physical stability as compared to the same activesubstances prepared using non-SEDS™ particle formation techniques.

[0089] Surface electric charge may be assessed as specific charge. Theelectrostatic charge carried by a particulate material may be measuredfor instance in a Faraday well. Alternatively the particulate materialmay for instance be subjected to triboelectrification by agitating itagainst an electrically conductive contact surface, for example in aturbula mixer or cyclone separator, and its charge and mass determinedboth before and after triboelectrification, suitably using anelectrometer, to give a value for specific charge. This process may alsobe used to give a measure of the adhesion properties of the particles,by measuring the mass of the original sample and that removable from themixer/separator in which it was agitated and calculating the weightpercentage of the sample lost by adhesion to the contact surface(s) ofthe vessel.

[0090] Adhesion may also be assessed using a simple test of the typedescribed in Examples 3 below, in which a sample is agitated in acontainer, and the non-adhering material then removed from the containerand weighed, to allow calculation of the percentage of the originalsample adhering to the container surfaces.

[0091] By way of example, an active substance according to the inventionpreferably has a mean specific charge of from −5 to +5 nCg⁻¹, morepreferably from −1 to +1 nCg⁻¹, and/or a mean specific charge which isat least 50%, preferably at least 70%, most preferably at least 80% or90% or 95%, lower than that of the same active substance produced by anon-SEDS™ particle formation process.

[0092] Following triboelectrification using a Turbula™ mixer, an activesubstance according to the invention preferably has a mean specificcharge which is at least 30% lower, more preferably at least 50% lower,most preferably at least 75% or 80% or 90% or 95% lower, than that ofthe same active substance produced by a non-SEDS™ process. Followingtriboelectrification using a cyclone separator, an active substanceaccording to the invention preferably has a mean specific charge whichis at least 30% lower, more preferably at least 50% lower, mostpreferably at least 75% or 80% or 85% lower, than that of the sameactive substance produced by a non-SEDS™ process.

[0093] The mean adhesion fraction (ie, the fraction of adhered material)assessed in the manner described above following triboelectrification ina turbula mixer, is preferably 20% w/w or less, more preferably 10% w/wor less, most preferably 5% or 2% w/w or less, for an active substanceaccording to the invention. It is preferably at least 50% lower, morepreferably at least 75% lower, most preferably at least 80% or 90%lower, for an active substance according to the invention than for thesame active substance produced by a non-SEDS™ process.

[0094] The mean adhesion fraction, assessed in the manner describedabove following triboelectrification in a cyclone separator, ispreferably 20% w/w or less, more preferably 10% w/w or less, mostpreferably 5% w/w or less, for an active substance according to theinvention. It is preferably at least 40% lower, more preferably at least50% lower, most preferably at least 60% or 65% lower, for an activesubstance according to the invention than for the same active substanceproduced by a non-SEDS™ process.

[0095] In cases, an active substance produced by a non-SEDS™ process mayexhibit at least 5 times as much adhesion as the same active substanceproduced by a SEDS™ process, preferably at least 8 times or at least 10times or at least 15 times that of the SEDS™ substance.

[0096] The adhesion force per unit area to a highly oriented pyrolyticgraphite substrate assessed using atomic force microscopy in the mannerdescribed above is preferably less than 60% of, more preferably lessthan 30% of, most preferably less than 15% of that for particles of thesame active substance produced by a non-SEDS™ process.

[0097] Powder flow properties may be assessed by analysing the dynamicavalanching behaviour of a particulate product, such as using anAeroflow™ powder avalanching apparatus (Amherst Process Instruments,Amherst, USA), for instance as described in the Examples below.

[0098] Superior powder flow properties, in an active substance accordingto the invention, may be manifested by a strange attractor plot which iscloser to the origin and/or has a smaller spread than that for the sameactive substance produced by a non-SEDS™ process. A strange attractorplot may be obtained, again as described in the examples below, frompowder avalanching data (in particular, time intervals betweenavalanches) using the method of Kaye et al, Part. Charact., 12 (1995),197-201. Substances according to the invention tend to exhibit lowermean avalanche times (for example at least 5% or even 8% lower at 100s/rev, at least 10% or even 14% lower at 145 s/rev) than correspondingproducts of non-SEDS™ processes. They may show a lower irregularity offlow (for example at least 5% or even 8% lower at 100 s/rev, at least 8%or even 10% lower at 145 s/rev) than corresponding non-SEDS™ products,irregularity of flow being assessed in terms of avalanche scatter.

[0099] The bulk powder density of an active substance according to theinvention may be measured in conventional manner, for example using avolumetric cylinder, and is preferably at least 20% lower, morepreferably at least 50% lower, most preferably at least 60% or 70% or80% lower, than that of the same active substance produced by anon-SEDS™ process. Its aerosolised powder bulk densityis preferably atleast 10%, more preferably at least 20%, lower. It has been found thatactive substances according to the invention may, surprisingly, haveboth relatively low bulk powder densities yet also good powder flowproperties in particular lower cohesiveness and adhesiveness and/or alower tendency to accumulate static charge.

[0100] Specific surface area of particles may be determined byconventional surface area measuring techniques such as low temperaturephysical adsorption of nitrogen (eg, BET nitrogen adsorption using aSurface Area Analyser Coulter™ SA 3100 (Coulter Corp., Miami, USA)).Preferably the specific surface area of a particulate active substanceaccording to the invention is at least 1.2 or 1.5 times, more preferablyat least twice, still more preferably at least 3 times, most preferablyat least 4 or 4.5 times, that of the same active substance produced by anon-SEDS™ process. Typically an active substance according to theinvention might have a specific surface area of at least 10 m²/g,preferably at least 15 or 20 or 25 m²/g, and/or a surface-to-volumeratio of at least twice, preferably at least 2.5 times, that ofspherical particles of the same volume diameter.

[0101] The shape factor f may suitably be calculated as f=Sv/Sv*, whereSv is the experimentally determined (eg, by BET nitrogen adsorption)specific surface area and Sv* the specific surface area calculated fromparticle size measurements (eg, those obtained by laser diffraction)assuming spherical particles. An active substance preferably has a shapefactor f which is at least 20%, more preferably at least 30%, largerthan that of the same active substance (suitably having the same or acomparable crystal shape and particle size) produced by a non-SEDS™particle formation process. Thus, particles of an active substanceaccording to the invention preferably have a higher available surfacearea than particles of the same active substance made by a non-SEDS™process—where for instance the particles are in the form of platelets orneedles, those of the present invention may thus be thinner than thoseproduced by non-SEDS™ techniques.

[0102] A typical shape factor f for a particulate active substanceaccording to the invention might for instance be 3 or greater,preferably 3.2 or greater, more preferably 3.5 or greater, mostpreferably 3.7 or greater.

[0103] A higher specific surface area and/or shape factor appears, in anactive substance according to the invention, to accompany improveddissolution performance as compared to the same active substanceproduced by a non-SEDS™ particle formation process. In particular, aproduct according to the invention may dissolve more rapidly in anygiven solvent and with greater efficiency, for instance with at least40% higher dissolution, more preferably at least 50% higher dissolutionthan the non-SEDS™ product after a period of 150 or even 300 minutes,ideally the SEDS™ product achieving complete dissolution after a periodof 50 minutes or less. Such improved dissolution is particularlyadvantageous for poorly soluble (generally poorly aqueous soluble)materials.

[0104] Surface roughness may be assessed using AFM analysis; reducedroughness may be indicated for instance by a reduced RMS roughness.Particles of an active substance according to the invention preferablyhave a RMS roughness, measured using AFM, of 0.5 nm or less, preferably0.3 or 0.2 nm or less. Their RMS roughness is preferably at least 70%lower, more preferably at least 80% or 90% lower, than that of the sameactive substance prepared by a non-SEDS™ particle formation process.

[0105] Deposition properties of an active substance, in particular fineparticle fractions, may be measured using the cascade impactortechnique, for instance using an Andersen™-type cascade impactor (CopleyScientific Ltd, Nottingham, UK). Such devices imitate particledeposition in the lungs from a dry powder inhaler. High fine particlefractions are preferred, with respect to delivery to stages 1 to 5 ofthe impactor. Thus, fine particle fractions are preferably measured asthe mass of particles having an efficient cut-off diameter (ECD) ofbetween 0.5 and 5 μm, for instance as described in the examples below.From the cascade impactor data, an apparent volume mean diameter mayalso be calculated as known in the art.

[0106] HPLC may be used for quantitative analysis of the activesubstance content in the material deposited at each stage of theimpactor and if applicable in associated apparatus such aspre-separator, throat or mouthpiece.

[0107] For the purpose of assessing fine particle fraction, the activesubstance of the invention may be blended with a suitable excipient,preferably a pharmaceutically acceptable excipient suitable for deliveryto the lung, a common example being lactose. Such a blend mighttypically contain from 1 to 10% w/w of the active substance, preferablyfrom 2 to 5% w/w. Again because of the advantageous properties of theactive substance of the invention, for instance its lower surface energyand adhesiveness, it tends to be better able to detach from theexcipient, under these conditions, than the same active substanceprepared by a non-SEDS™ process; in other words, it forms less strongaggregates with the excipient.

[0108] The active substance of the invention is preferably in the formof solid (eg, as opposed to hollow, porous or at least partiallyfluid-containing) particles. It is preferably in a crystalline orsemi-crystalline (as opposed to amorphous) form, more preferablycrystalline.

[0109] In particular it preferably has a crystalline form which issignificantly longer in one dimension than in at least one otherdimension (ie, it has a relatively high aspect ratio); this embraces forexample needle-like crystals and also, potentially, wafer-, blade- orplate-like crystals (which are longer in two dimensions than in thethird) and elongate prism-shaped crystals. These have been found to showbetter DPI performance than correspondingly sized particles of othershapes. Needle-like (acicular) or platelet-shaped crystals may beparticularly preferred.

[0110] In the above discussion, “significantly” longer means at least5%, preferably at least 10% or 20% or 30%, greater than the length ofthe lower of the two parameters being compared.

[0111] As discussed above, particles according to the invention if inthe form of platelets or needles are typically thinner than those of thesame active substance produced by a non-SEDS™ process (as reflected byfor instance a difference in shape factors, shape coefficients andspecific surface areas). When examined for example by SEM, the particlesof the invention can often be seen to have less rounded edges andcorners and/or to be less fragmented than those of the non-SEDS™substance in particular a micronised substance—this may be reflected ina lower surface energy, lower particle adhesion and/or lower tendencyfor aggregation in the product of the invention.

[0112] In general, the behaviour of an active substance according to thepresent invention on aerosolisation, which in turn affects itssuitability for respiratory drug delivery and in particular for DPIdelivery, may be assessed and characterised using the techniquesoutlined in the examples below. These can involve assessing the size,surface characteristics, aerodynamic properties, deagglomerationbehaviour and/or solid state properties of the active substanceparticles. Such techniques may be used for instance in the selectionmethod of the second aspect of the invention.

[0113] By “active substance” is meant a substance capable of performingsome useful function in an end product, whether pharmaceutical,pesticidal or whatever. The term is intended to embrace substances whosefunction may be as an excipient for another substance.

[0114] The active substance may be a single active substance or amixture of two or more. It may be monomeric, oligomeric or polymeric,organic (including organometallic) or inorganic, hydrophilic orhydrophobic. It may be a small molecule, for instance a synthetic druglike paracetamol, or a macromolecule such as a protein or peptide(including enzymes, hormones, antibodies and antigens), nucleotide,nucleoside or nucleic acid. Other potential active substances includevitamins, amino acids, lipids including phospholipids and aminolipids,carbohydrates such as polysaccharides, cells and viruses.

[0115] The active substance preferably comprises (more preferably is) apharmaceutically or nutriceutically active substance, or apharmaceutically or nutriceutically acceptable excipient, or a mixtureof two or more thereof. More preferably it is a pharmaceutically activesubstance or mixture thereof which is suitable for delivery byinhalation (which term includes nasal and/or oral inhalation), althoughin general it may be any active substance which is deliverable as a drypowder, ideally using a passive dry powder inhaler. Many other activesubstances, whatever their intended function (for instance, herbicides,pesticides, foodstuffs, imaging agents, dyes, perfumes, cosmetics andtoiletries, detergents, coatings, products for use in the ceramics,photographic or explosives industries, etc.) are embraced by the presentinvention.

[0116] Of particular interest for delivery by inhalation arepharmaceutically active substances which need to be deliveredsystemically and require rapid onset of action. According to a preferredembodiment, formulations are provided which achieve a maximumconcentration of a pharmaceutically active substance, C_(max), within 1hour of administration, preferably within 30 minutes, and mostpreferably within 15 minutes. This time to achieve maximum concentrationof the active substance is referred to herein as T_(max).

[0117] Examples of pharmaceutically active substances which may bedelivered by inhalation include β₂-agonists, steroids such asglucocorticosteroids (preferably anti-inflammatories),anti-cholinergics, leukotriene antagonists, leukotriene synthesisinhibitors, pain relief drugs generally such as analgesics andanti-inflammatories (including both steroidal and non-steroidalanti-inflammatories), cardiovascular agents such as cardiac glycosides,respiratory drugs, anti-asthma agents, bronchodilators, anti-canceragents, alkaloids (eg, ergot alkaloids) or triptans such as can be usedin the treatment of migraine, drugs (for instance sulphonyl ureas)useful in the treatment of diabetes and related disorders, sleepinducing drugs including sedatives and hypnotics, psychic energizers,appetite suppressants, anti-arthritics, anti-malarials, anti-epileptics,anti-thrombotics, anti-hypertensives, anti-arrhythmics, anti-oxicants,anti-depressants, anti-psychotics, auxiolytics, anti-convulsants,anti-emetics, anti-infectives, anti-histamines, anti-fungal andanti-viral agents, drugs for the treatment of neurological disorderssuch as Parkinson's disease (dopamine antagonists), drugs for thetreatment of alcoholism and other forms of addiction, drugs such asvasodilators for use in the treatment of erectile dysfunction, musclerelaxants, muscle contractants, opioids, stimulants, tranquilizers,antibiotics such as macrolides, aminoglycosides, fluoroquinolones andbeta-lactams, vaccines, cytokines, growth factors, hormonal agentsincluding contraceptives, sympathomimetics, diuretics, lipid regulatingagents, antiandrogenic agents, antiparasitics, anticoagulants,neoplastics, antineoplastics, hypoglycemics, nutritional agents andsupplements, growth supplements, antienteritis agents, vaccines,antibodies, diagnostic agents, and contrasting agents and mixtures ofthe above (for example the asthma combination treatment containing bothsteroid and β-agonist). More particularly, the active agent may fallinto one of a number of structural classes, including but not limited tosmall molecules (preferably insoluble small molecules), peptides,polypeptides, proteins, polysaccharides, steroids, nucleotides,oligonucleotides, polynucleotides, fats, electrolytes, and the like.

[0118] Specific examples include the β₂-agonists salbutamol (eg,salbutamol sulphate) and salmeterol (eg, salmeterol xinafoate), thesteroids budesonide and fluticasone (eg, fluticasone propionate), thecardiac glycoside digoxin, the alkaloid anti-migraine drugdihydroergotamine mesylate and other alkaloid ergotamines, the alkaloidbromocriptine used in the treatment of Parkinson's disease, sumatriptan,rizatriptan, naratriptan, frovatriptan, almotriptan, zolmatriptan,morphine and the morphine analogue fentanyl (eg, fentanyl citrate),glibenclamide (a sulphonyl urea), benzodiazepines such as vallium,triazolam, alprazolam, midazolam and clonazepam (typically used ashypnotics, for example to treat insomnia or panic attacks), theanti-psychotic agent risperidone, apomorphine for use in the treatmentof erectile dysfunction, the anti-infective amphotericin B, theantibiotics tobramycin, ciprofloxacin and moxifloxacin, nicotine,testosterone, the anti-cholenergic bronchodilator ipratropium bromide,the bronchodilator formoterol, monoclonal antibodies and the proteinsLHRH, insulin, human growth hormone, calcitonin, interferon (eg, β- orγ-interferon), EPO and Factor VIII, as well as in each casepharmaceutically acceptable salts, esters, analogues and derivatives(for instance prodrug forms) thereof.

[0119] Additional examples of active agents suitable for practice withthe present invention include but are not limited to aspariginase,amdoxovir (DAPD), antide, becaplermin, calcitonins, cyanovirin,denileukin diftitox, erythropoietin (EPO), EPO agonists (e.g., peptidesfrom about 10-40 amino acids in length and comprising a particular coresequence as described in WO 96/40749), domase alpha, erythropoiesisstimulating protein (NESP), coagulation factors such as Factor VIIa,Factor VIII, Factor IX, von Willebrand factor; ceredase, cerezyme,alpha-glucosidase, collagen, cyclosporin, alpha defensins, betadefensins, exedin-4, granulocyte colony stimulating factor (GCSF),thrombopoietin (TPO), alpha-1 proteinase inhibitor, elcatonin,granulocyte macrophage colony stimulating factor (GMCSF), fibrinogen,filgrastim, growth hormones, growth hormone releasing hormone (GHRH),GRO-beta, GRO-beta antibody, bone morphogenic proteins such as bonemorphogenic protein-2, bone morphogenic protein-6, OP-1; acidicfibroblast growth factor, basic fibroblast growth factor, CD-40 ligand,heparin, human serum albumin, low molecular weight heparin (LMWH),interferons such as interferon alpha, interferon beta, interferon gamma,interferon omega, interferon tau; interleukins and interleukin receptorssuch as interleukin-1 receptor, interleukin-2, interluekin-2 fusionproteins, interleukin-1 receptor antagonist, interleukin-3,interleukin-4, interleukin-4 receptor, interleukin-6, interleukin-8,interleukin-12, interleukin-13 receptor, interleukin-17 receptor;lactoferrin and lactoferrin fragments, luteinizing hormone releasinghormone (LHRH), insulin, pro-insulin, insulin analogues (e.g.,mono-acylated insulin as described in U.S. Pat. No. 5,922,675), amylin,C-peptide, somatostatin, somatostatin analogs including octreotide,vasopressin, follicle stimulating hormone (FSH), influenza vaccine,insulin-like growth factor (IGF), insulintropin, macrophage colonystimulating factor (M-CSF), plasminogen activators such as alteplase,urokinase, reteplase, streptokinase, pamiteplase, lanoteplase, andteneteplase; nerve growth factor (NGF), osteoprotegerin,platelet-derived growth factor, tissue growth factors, transforminggrowth factor-1, vascular endothelial growth factor, leukemia inhibitingfactor, keratinocyte growth factor (KGF), glial growth factor (GGF), TCell receptors, CD molecules/antigens, tumor necrosis factor (TNF),monocyte chemoattractant protein-1, endothelial growth factors,parathyroid hormone (PTH), glucagon-like peptide, somatotropin, thymosinalpha 1, thymosin alpha 1 Ilb/IlIa inhibitor, thymosin beta 10, thymosinbeta 9, thymosin beta 4, alpha-1 antitrypsin, phosphodiesterase (PDE)compounds, VLA-4 (very late antigen-4), VLA-4 inhibitors,bisphosponates, respiratory syncytial virus antibody, cystic fibrosistransmembrane regulator (CFTR) gene, deoxyreibonuclease (Dnase),bactericidal/permeability increasing protein (BPI), and anti-CMVantibody. Exemplary monoclonal antibodies include etanercept (a dimericfusion protein consisting of the extracellular ligand-binding portion ofthe human 75 kD TNF receptor linked to the Fc portion of IgG1),abciximab, afeliomomab, basiliximab, daclizumab, infliximab, ibritumomabtiuexetan, mitumomab, muromonab-CD3, iodine 131 tositumomab conjugate,olizumab, rituximab, and trastuzumab (herceptin), amifostine,amiodarone, aminoglutethimide, amsacrine, anagrelide, anastrozole,asparaginase, anthracyclines, bexarotene, bicalutamide, bleomycin,buserelin, busulfan, cabergoline, capecitabine, carboplatin, carmustine,chlorambucin, cisplatin, cladribine, clodronate, cyclophosphamide,cyproterone, cytarabine, camptothecins, 13-cis retinoic acid, all transretinoic acid; dacarbazine, dactinomycin, daunorubicin, dexamethasone,diclofenac, diethylstilbestrol, docetaxel, doxorubicin, epirubicin,estramustine, etoposide, exemestane, fexofenadine, fludarabine,fludrocortisone, fluorouracil, fluoxymesterone, flutamide, gemcitabine,epinephrine, L-Dopa, hydroxyurea, idarubicin, ifosfamide, imatinib,irinotecan, itraconazole, goserelin, letrozole, leucovorin, levamisole,lomustine, mechlorethamine, medroxyprogesterone, megestrol, melphalan,mercaptopurine, methotrexate, metoclopramide, mitomycin, mitotane,mitoxantrone, naloxone, nicotine, nilutamide, octreotide, oxaliplatin,pamidronate, pentostatin, pilcamycin, porfimer, prednisone,procarbazine, prochlorperazine, ondansetron, raltitrexed, sirolimus,streptozocin, tacrolimus, tamoxifen, temozolomide, teniposide,testosterone, tetrahydrocannabinol, thalidomide, thioguanine, thiotepa,topotecan, tretinoin, valrubicin, vinblastine, vincristine, vindesine,vinorelbine, dolasetron, granisetron; formoterol, fluticasone,leuprolide, midazolam, alprazolam, amphotericin B, podophylotoxins,nucleoside antivirals, aroyl hydrazones, sumatriptan; macrolides such aserythromycin, oleandomycin, troleandomycin, roxithromycin,clarithromycin, davercin, azithromycin, flurithromycin, dirithromycin,josamycin, spiromycin, midecamycin, leucomycin, miocamycin, rokitamycin,andazithromycin, and swinolide A; fluoroquinolones such asciprofloxacin, ofloxacin, levofloxacin, trovafloxacin, alatrofloxacin,moxifloxicin, norfloxacin, enoxacin, grepafloxacin, gatifloxacin,lomefloxacin, sparfloxacin, temafloxacin, pefloxacin, amifloxacin,fleroxacin, tosufloxacin, prulifloxacin, irloxacin, pazufloxacin,clinafloxacin, and sitafloxacin; aminoglycosides such as gentamicin,netilmicin, paramecin, tobramycin, amikacin, kanamycin, neomycin, andstreptomycin, vancomycin, teicoplanin, rampolanin, mideplanin, colistin,daptomycin, gramicidin, colistimethate; polymixins such as polymixin B,capreomycin, bacitracin, penems; penicillins includingpenicllinase-sensitive agents like penicillin G, penicillin V;penicllinase-resistant agents like methicillin, oxacillin, cloxacillin,dicloxacillin, floxacillin, nafcillin; gram negative microorganismactive agents like ampicillin, amoxicillin, and hetacillin, cillin, andgalampicillin; antipseudomonal penicillins like carbenicillin,ticarcillin, azlocillin, mezlocillin, and piperacillin; cephalosporinslike cefpodoxime, cefprozil, ceftbuten, ceftizoxime, ceftriaxone,cephalothin, cephapirin, cephalexin, cephradrine, cefoxitin,cefamandole, cefazolin, cephaloridine, cefaclor, cefadroxil,cephaloglycin, cefuroxime, ceforanide, cefotaxime, cefatrizine,cephacetrile, cefepime, cefixime, cefonicid, cefoperazone, cefotetan,cefmetazole, ceftazidime, loracarbef, and moxalactam, monobactams likeaztreonam; and carbapenems such as imipenem, meropenem, pentamidineisethiouate, albuterol sulfate, lidocaine, metaproterenol sulfate,beclomethasone diprepionate, triamcinolone acetamide, budesonideacetonide, fluticasone, ipratropium bromide, flunisolide, cromolynsodium, and ergotamine tartrate; taxanes such as paclitaxel; SN-38, andtyrphostines.

[0120] The above exemplary biologically active agents are meant toencompass, where applicable, analogues, agonists, antagonists,inhibitors, isomers, and pharmaceutically acceptable salt forms thereof.In reference to peptides and proteins, the invention is intended toencompass synthetic, recombinant, native, glycosylated,non-glycosylated, and biologically active fragments and analogs thereof.

[0121] The active substance may comprise two or more active substancesformulated together, such as one coated with another, or one dispersedwithin a matrix of another, or a physical mixture (blend) of two ormore. Common examples of such formulations include two or morecoformulated pharmaceutical actives, or pharmaceutically activesubstances coated with excipients, or physical mixtures ofpharmaceutically active substances with excipients such as in particularlactose, or solid dispersions of pharmaceutically active substances withexcipients, the excipient often being present to modify the release rateand/or to target delivery of the pharmaceutical. However, in general theactive substances of the invention will exhibit improved dispersibilityand DPI performance in the absence of excipients, ie, in the form of theactive substance alone (for example in the form of a drug or drugswithout excipients).

[0122] The improved dispersibility and DPI performance is preferablyalso exhibited in the absence of dispersion-enhancing or stabilisingadditives, such as surfactants or lubricants.

[0123] Preferably a particulate active substance according to theinvention will exhibit improved dispersibility and DPI performance ascompared to the same active substance, in particulate form, prepared bya non-SEDS™ particle formation process, in particular micronisation orgranulation. By “micronisation” is meant a process involving mechanicalmeans, for instance milling or grinding, to reduce particle size to themicrometer range. The non-SEDS™ substance may comprise particles havingthe same or a smaller size (for instance, 90% or less of the size of, orpreferably 80% or 70% or 60% or less of the size) than those of theactive substance of the invention.

[0124] In certain cases, an active substance according to the presentinvention may be a pharmaceutically active substance or apharmaceutically acceptable excipient (preferably a substance suitablefor and/or intended for delivery by inhalation) other than salmeterolxinafoate (alone or coformulated with hydroxypropyl cellulose);ct-lactose monohydrate; R-TEM β-lactamase; maltose; trehalose; sucrose;budesonide; salbutamol sulphate; nicotinic acid; paracetamol (alone orcoformulated with salmeterol xinafoate, L-poly(lactic acid), ethylcellulose (EC), hydroxypropyl methyl cellulose (HPMC) or poly vinylpyrrolidone (PVP)); ibuprofen; ketoprofen (alone or coformulated withEC, HPMC or PVP); salicylic acid; either indomethacin, carbamazepine,theophylline, ascorbic acid or a COX-2 selective inhibitor coformulatedwith EC, HPMC or PVP; quinine sulphate coformulated with EC; fluticasonepropionate; omeprazole magnesium tetrahydrate; (S)-omeprazole magnesiumtrihydrate; formoterol fumarate dihydrate; felodipine; candesartancilexetil; lysozyme; albumin; insulin; terbutaline sulphate; fenoterolhydrobromide; dihydroergotamine mesylate; and/orrisperidone-(9-hydroxy)-palmitate.

[0125] It has been found that particulate active substances whichexhibit the improved DPI performance and other advantageous propertiesdescribed above can be produced using the so-called SEDS™ (“SolutionEnhanced Dispersion by Supercritical fluid”) process, which is a versionof the GAS process referred to above.

[0126] SEDS™ is a process for forming particles of a “target” substance.It involves contacting a solution or suspension of the target substancein a fluid vehicle (the “target solution/suspension”) with an excess ofa compressed fluid (generally a supercritical or near-critical fluid)anti-solvent under conditions which allow the anti-solvent to extractthe vehicle from the target solution/suspension and to cause particlesof the target substance to precipitate from it. The conditions are suchthat the fluid mixture thus formed between the anti-solvent and theextracted vehicle is still in a compressed or supercritical ornear-critical state. The anti-solvent fluid should be a nonsolvent forthe target substance and be miscible with the fluid vehicle.

[0127] Carrying out a SEDS™ process specifically involves using theanti-solvent fluid simultaneously both to extract the vehicle from, andto disperse, the target solution/suspension. In other words, the fluidsare contacted with one another in such a manner that the mechanical(kinetic) energy of the anti-solvent can act to disperse the targetsolution/suspension at the same time as it extracts the vehicle.“Disperse” in this context refers generally to the transfer of kineticenergy from one fluid to another, usually implying the formation ofdroplets, or of other analogous fluid elements, of the fluid to whichthe kinetic energy is transferred.

[0128] Suitable SEDS™ processes are described in WO-95/01221,WO-96/00610, WO-98/36825, WO-99/44733 and WO-99/59710, WO-01/03821 andWO-01/15664, in our co-pending PCT patent application no. PCT/GBPCT/GB01/04873 and in our co-pending UK patent application no.0117696.5. Other suitable SEDS™ processes are described in WO-99/52507,WO-99/52550, WO-00/30612, WO-00/30613 and WO-00/67892, all of which arehereby incorporated in their entirety by reference.

[0129] In SEDS™, the target solution/suspension and the anti-solvent arepreferably contacted with one another in the manner described inWO-95/01221 and/or WO-96/00610, being co-introduced into a particleformation vessel using a fluid inlet means which allows the mechanicalenergy (typically the shearing action) of the anti-solvent flow tofacilitate intimate mixing and dispersion of the fluids at the pointwhere they meet. The target solution/suspension and the anti-solventpreferably meet and enter the particle formation vessel at substantiallythe same point, for instance via separate passages of a multi-passagecoaxial nozzle.

[0130] A particulate active substance according to the first aspect ofthe present invention is preferably prepared using a SEDS™ process, suchas one or a combination of those described in the above documents.Preferred features of the process may be as described below inconnection with the fourth aspect of the invention. The active substancemay thus be insoluble or only sparingly soluble in water. It ispreferably insoluble or only sparingly soluble in compressed (eg,supercritical or near-critical) carbon dioxide. Such materials lendthemselves particularly well to SEDS™ processing and indeed are oftendifficult to process using other particle formation techniques such asspray drying or freeze drying.

[0131] Thus, a fourth aspect of the present invention provides the useof a SEDS™ process (as described above) to produce an active substancein particulate form, for the purpose of improving the dispersibility ofthe substance and/or its performance in a passive dry powder deliverydevice, and/or for the purpose of achieving one or more of thecharacteristics (a) to (q), optionally in combination with one or moreof the other preferred properties, listed above in connection with thefirst aspect of the invention.

[0132] The process is preferably carried out using supercritical ornear-critical, more preferably supercritical, CO₂ as the anti-solvent.The choice of operating conditions such as temperature, pressure andfluid flow rates, and the choice of solvent and of anti-solvent modifierif necessary, will depend on the nature of the active substance, forinstance its solubility in the fluids present and, if it can exist indifferent polymorphic forms, which form is to be precipitated.Generally, the conditions should be chosen to minimise or reduceparticle sizes and/or size distributions—this will generally meanselecting a higher anti-solvent flow rate (eg, a targetsolution/suspension: anti-solvent flow rate ratio (at or immediatelyprior to the two fluids coming into contact with one another) of 0.03 orless, preferably 0.02 or less or even 0.01 or less), and/or a higheroperating temperature (eg, from 50 to 100° C., preferably from 70 to 90°C., especially for a CO₂ anti-solvent), and/or a higher operatingpressure (eg, from 80 to 210 bar, preferably from 90 to 200 bar, againespecially for a CO₂ anti-solvent).

[0133] The process conditions are also ideally chosen to maximise orenhance the purity (which may be the polymorphic or enantiomeric purity)of the product—this will involve the use of a vehicle, anti-solvent,temperature and pressure suitable to maximise or enhance selectivity ofprecipitation of the desired substance from those present in the targetsolution/suspension.

[0134] The operating conditions for the process (in particular thetarget solution/suspension concentration and the relative flow rates ofthe target solution/suspension and anti-solvent) are preferablyselected, for any particular set of reagents (including the fluidvehicle and anti-solvent) and particle formation vessel and fluid inletgeometry, so as to maximise or enhance the degree of supersaturation inthe target solution/suspension flow at its point of contact with theanti-solvent. This may be effected for instance in the manner describedin the examples below, using solubility measurements to determine theoptimum operating conditions.

[0135] The product of the fourth aspect of the invention is preferably aparticulate active substance according to the first aspect.

[0136] Improving the performance of a substance in a passive dry powderdelivery device will typically mean increasing the fine particlefraction in the emitted dose when the active substance is deliveredusing a passive dry powder inhaler. The improvement may for instance beas compared to the performance of the substance prior to the SEDS™processing, and/or of the same substance (preferably having the sameparticle size or a particle size no more than 10% or 20% or 30% or 40%different) when produced using another particle formation process suchas micronising, granulation or conventional spray drying.

[0137] According to a fifth aspect of the present invention, there isprovided an active substance for use in a method of surgery, therapy ordiagnosis practised on a human or animal body, in which method thesubstance is delivered to a patient using a passive dry powder inhaleror analogous delivery device, wherein the substance has one or more ofthe properties described above in connection with the first to thefourth aspects of the invention.

[0138] A sixth aspect of the invention provides the use of an activesubstance in the manufacture of a medicament for use in a passive drypowder inhaler or analogous delivery device, wherein the substance hasone or more of the properties described above in connection with thefirst to the fourth aspects of the invention.

[0139] For the fifth and sixth aspects of the invention, the activesubstance is preferably an active substance according to the firstaspect, and is preferably prepared using the method of the fourth aspectand/or selected using the method of the second aspect. It is preferablya pharmaceutically or nutriceutically active substance. Other preferredfeatures of the fifth and sixth aspects of the invention may be asdescribed in connection with the first to the fourth aspects.

[0140] A seventh aspect of the present invention provides a dosageformulation or collection thereof, for use in a drug delivery devicesuch as in particular a dry powder inhaler, the dosage formulationcontaining a particulate active substance according to the first aspectof the invention. Preferably the formulation consists essentially of theactive substance, ie, it contains 95% w/w, preferably 98% w/w or 99%w/w, or more of the active substance. In particular, it may consistessentially of a pharmaceutically active substance in the absence ofexcipients and/or of dispersion enhancing or stabilising additives.

[0141] An eighth aspect of the invention provides an active substance(eg, drug) delivery device, preferably an inhaler, which contains one ormore dosage formulations of an active substance according to the firstaspect. The delivery device is preferably of the type designed todeliver a predetermined dose of an active substance in a dry (ie,without a fluid carrier) particulate form, for instance a dry powderinhaler and in particular a passive dry powder inhaler. It may containone or more dosage formulations according to the seventh aspect of theinvention.

[0142] According to a ninth aspect, the invention provides a method fordelivering an active substance, the method involving charging a deliverydevice, in particular a device according to the eighth aspect of theinvention, with an active substance and/or a formulation according tothe invention and/or an active substance selected in accordance with thesecond aspect of the invention.

[0143] A tenth aspect provides a method of treatment of a human oranimal patient, which method involves administering to the patient,preferably using the method of the ninth aspect of the invention, anactive substance and/or a formulation according to the invention and/oran active substance selected in accordance with the second aspect of theinvention.

[0144] Both of these methods preferably involve the use of a deliverydevice such as an inhaler, more preferably a delivery device accordingto the eighth aspect of the invention. The active substance preferablycomprises a pharmaceutically active substance suitable for inhalationtherapy.

[0145] The present invention will now be illustrated with reference tothe following examples, which show how a SEDS™ process may be used toprepare particulate active substances with advantageous properties foruse in passive dry powder inhalers.

EXAMPLES

[0146] The system used to carry out the SEDS™ particle formationprocesses was of the general type shown schematically in the figures ofWO-95/01221.

Example 1

[0147] The SEDS™ method described in WO 95/01221 was employed to preparepowders of salmeterol xinafoate (SX, GlaxoSmithKline), terbutalinesulphate (TBS, AstraZeneca) and fenoterol hydrobromide (FHBr, BoehringerIngelheim). The particle formation vessel of 0.5 L volume was used inall cases. Several solvents including methanol. Ethanol, acetone andtetrahydrofurane were tested. Typical flow rate of CO₂ was 5 kg/hour.

[0148] Analytical Methods

[0149] PSD measurements were performed using firstly, AeroSizertime-of-flight instrument equipped with AeroDisperser™ (TSI Inc.,Minneapolis. USA) and secondly, laser diffraction sensor Helos withdry-powder air-dispersion system Rodos (Sympatec GmbH. Germany). Thevolume mean particle diameter, VMD, was obtained for both instrumentsusing software options. In the general case of non-spherical particles,these instruments cannot provide the exact value of VMD, however, thetime-of-flight technique gives an aerodynamic-equivalent particlediameter, whereas the laser diffraction method provides the geometricprojection-equivalent diameter. These diameters afford the complementaryinformation on PSD and therefore can be used for comparative sizeanalysis.

[0150] For SX powders, inverse gas chromatography (IGC) was performedusing a Hewlett Packard Series 5890 Gas Chromatograph equipped with anintegrator and flame ionization detector. For TBS and FHBr powders, IGCwas done using a Hewlett Packard Series 6890 instrument which wasspecifically modified for IGC measurements by Surface MeasurementSystems Ltd (Manchester, UK). The IGC method is described in detail byTong et al. 2001. (Tong H. H. Y., B. Y. Shekunov, P. York, A. H. L.Chow, 2001. Pharm. Res. 18, 852.) Triplicate measurements in separatepacked columns were made. Differences in surface energetics werereflected in the calculated dispersive component of the surface freeenergy, γ_(S) ^(D), specific component of surface free energies ofadsorption. ΔG_(A); the acid-base parameters, K_(A) and K_(O). and thetotal (Hildebrand) solubility parometer, δ, which reflects the adhesionwork between particles. The γ_(S) ^(D) and ΔG_(A) values were obtainedat 303K.

[0151] The deposition behaviour of micronised andsupercritically-produced powders were evaluated using an Andersen-typecascade impactor (Copley Scientific Limited, Nottingham. UK). Thisdevice is designed to imitate particle deposition in the lungs; thecontrol criterion is that the high fine particle fraction (FPF) of arespirable drug to be delivered to the defined stages (from 1 to 5) ofthe cascade impactor. The drugs were blended with inhalation grade, DMVPharmatose® 325M α-lactose monohydrate, with 3.8% w/w of drug typicalfor such formulation. The airflow through the apparatus measured at theinlet to the throat, was adjusted to produce a pressure drop of 4 kPaover the inhaler under test (Clickhaler™) according to compendialguidelines, consistent with the flow rate 49 L/min.

[0152] Several batches of particulate material of respirable size withcumulative PSD for all batches X₉₉<10 μm were consistently prepared,with batch quantities between 1 and 10 g. VMD of powders obtained usingdifferent techniques are shown in Table 1. TABLE 1 VMD (μm) VMD (μm)Compound (Time of flight) (laser diffraction) FPF % SX 1.2 1.69 25.1Micronised SX 1.6 3.56 57.8 SEDS TSB 2.7 3.04 30.7 Micronised TSB 3.43.43 38.6 SEDS FHBr 1.7 2.34 17.4 Micronised FHBr 1.7 3.55 41.7 SEDS

[0153] These data indicate that although both the aerodynamic (time offlight) and geometric (laser diffraction) diameters for the micronisedpanicles are smaller than the correspondent VMD for supercritically-produced materials, the FPF deposited in the cascade impactor issignificantly larger for the supercritically-produced powders. Thereforethe powder dispersion rather than the particle size distribution definesthe deposition profile of the drug particles in this aerosol test.Dispersability of powders in the air flow is defined by the balance offorces generated by the aerodynamic stresses and the inter-particulateforces. The theoretical tensile strength of the particle aggregate,required to separate primary particles, is proportional to the work ofparticle adhesion (Kendell and Stainton. 2001) and can be associatedwith the specific surface energy defined by the IGC method. Table 2represents the surface-energy related parameters which reflect theinteraction of the non-polar γ_(S) ^(D) and polar ΔG_(A) nature. TABLE 2ΔG_(A) (kJ/mol) γ_(s) ^(D) Diethyl ethyl Substance (mJ/m²) ether tolueneacetone acetate chloroform dioxane SX 40.49 14.20 15.24 17.46 14.78 Micronised SX 34.55 12.65 (0.08) (0.06) (0.24) SEDS TSB 58.61 3.42 12.5716.01 1.79 15.96 Micronised TSB 55.05 2.85 10.42 13.76 1.21 14.20 SEDSFHBr 48.53 4.77 0.69 Micronised FHBr 49.87 3.86 13.15 17.48 0.63 15.32SEDS

[0154] The reduced magnitude of γ_(S) ^(D) for thesupercritically-produced powders implies that the surfaces of theseparticles are less energetic for non-polar, dispersive surfaceinteractions than the micronised materials. The largest changes arehowever observed for the polar interactions ΔG_(A) which aresignificantly smaller, by a factor of 1.5 on average, for thesupercritically-produced powders. In general, the enhanced powderdispersion always correlated well with the reduced surface energy ofthese materials.

Example 2

[0155] Salmeterol xinafoate (SX) (GlaxoWellcome, Ware UK) in the form ofgranulated material (G-SX) used for micronisation and micronised powder(M-SX). HPLC grade solvent was purchased from BDH Chemicals, Leicester,UK. All analytical grade liquid probes used in IGC studies werepurchased from Labscan. Dublin, Ireland. Industrial grade (>99.95% pure)CO₂ was supplied by Air Products (Manchester, UK).

[0156] The SEDS™ method was employed to prepare powders of SX form I(S-SX). This technique is based on mixing between supercritical CO2antisolvent and a drug solution using a twin-fluid nozzle as more fullydescribed in WO 95/01221 cited above. Methanol, acetone andtetrahydrofurane were tested in this work. The particle formation vessel(500 ml volume) with the nozzle was placed in an air-heated oven. Thetemperature in the vessel was monitored by a thermocouple with accuracy±0.1° C. and was kept constant at 40° C. Pressure in the vessel wascontrolled by an air-actuated back-pressure regulator (26-1761 withER3000 electronic controller, Tescom. Elk River, Minn., USA) and keptconstant at 250±1 bar. The difference in the inlet and outlet pressurewas typically within 1% of its absolute value. The CO2 flow rate,supplied by a water-cooled diaphragm pump Milton Roy B (Dosapro MiltonRoy, Pont-Saint-Pierre, France) was typically between 25 and 50 NL/minas monitored after expansion using a gas flow meter (SHO-Meter 1355,Brooks Instruments B. V., Veenendal, Holland) and also controlled beforeexpansion using high-pressure liquid flow meter (DK34, KrohmeMesstechnik GmbH, Duisburg, Germany). Solution concentration of SXvaried between 1 and 10% w/v. Solution flow rate was provided by ametering pump PU-980 (Jasco Co, Tokyo, Japan) and varied from 0.5 to 10ml/min.

[0157] Several batches were prepared with batch quantities between 1 and10 g. The obtained cumulative PSD for all batches had X₉₀=10 μm andvolume-moment mean particle diameter, d_(4.3)≈5 μm, as determined usingthe laser diffraction (LD) method.

[0158] Inverse gas chromatography (IGC) was performed on a HewlettPackard Series II 5890 Gas) Chromatograph (Hewlett Packard, Wilmington,Del., USA) equipped with an integrator and flame ionization detector.Injector and detector temperatures were maintained at 100 and 150° C.respectively. Glass columns (60 cm long and 3.5 mm i.d.) weredeactivated with 5% solution of dimethyldichlorosilane in toluene beforebeing packed with SX powder. The columns were plugged with silanisedglass wool at both ends and maintained at 40° C. Data were obtained fora known weight and surface area of the sample using a nitrogen gas(purity>99.995%) flow at 20.0 ml/min. The column was weighed before andafter the experiment to ensure no loss of materials during the run.Trace amount of vapour from non-polar and polar probes was injected. Theretention times and volumes of the injected probes were measured atinfinite dilution and thus were independent of the quantity of probesinjected. The non-polar probes employed were pentane, hexane, heptane,octane and nonane: the polar probes were dichloromethane, chloroform,acetone, ethyl acetate, tetrahydrofuran and diethyl ether. Triplicatemeasurements in separate columns were made for G-SX. M-SX and S-SXpowders. Differences in surface energetics were reflected in thecalculated dispersive component of the surface free energy, γ_(S) ^(D);specific component of surface free energies of adsorption, −ΔG_(A)^(sp), and the acid-base parameters, K_(A), and K_(D).

[0159] Data on specific surface areas required for IGC studies weredetermined by BET nitrogen adsorption using a Surface Area AnalyzerCoulter SA 3100 (Coulter Corp., Miami, Fla., USA). Samples were placedin glass sample holders and out-gassed with helium (purity>99.999%) at40° C. for 16 hours before analysis. Nitrogen (purity>99.999%) was usedas adsorbate and BET surface area was recorded as specific surface areaof the samples. All measurements were performed in triplicate using thesame batch of each material.

[0160] Electric Charge and Adhesion Measurements

[0161] Triboelectrification was undertaken against a stainless steelcontact surface using either a turbula mixer or a cyclone separator.Triboelectrification in a turbula mixer (Glen Creston, UK) was carriedout by agitating a powder sample for 5 minutes at 30 rpm in a 100 mlstainless steel vessel at ambient temperature and relative humidity. Asample was poured in a reproducible manner into a Faraday well connectedto an electrometer (Keithley 610, Keithley Instruments, Reading, UK).Charge and mass of sample was then recorded to give specific chargebefore and after triboelectrification. % w/w adhesion to the innersurface of the mixing vessel was calculated from the original mass ofsample and the mass of sample poured into the Faraday well. Duringtriboelectrification in a cyclone separator, a powder was fed from asteel vibratory table into a venturi funnel. Compressed air (velocity 8m/s. relative humidity below 10%, ambient temperature) was used toconvey the powder from the venturi along a horizontal pipe into thecyclone separator. The Faraday well and force compensation load cell wasfitted at the base of the cyclone and used to collect charged particles.Final specific charge was recorded for non-adhered powder residing inthe Faraday well and, where possible, powder adhering to the cyclonewall was dislodged by a stream of air and its charge and mass recorded.In both cases, the results were obtained from triplicate measurements.

[0162] Particle Size Analysis

[0163] The instrument consisted of laser diffraction sensor HELOS anddry-powder air-dispersion system RODOS (Sympatec GmbH. Germany) withWINDOX OS computer interface. The dispersion process was controlled bymeans of adjusting pressure of the compressed air flow between 0.5 and 5bar. The pressure of 2 bar was found to be sufficient to disperse mostof the agglomerates avoiding, at the same time, attrition of the primaryparticles. All measurements were performed in triplicate. The particleshape factor, f, was calculated asf=Sv/Sv*. where Sv is the experimentalspecific surface area and Sv* is the specific surface area determinedusing the LD instrument assuming the particle sphericity.

[0164] Results and Discussion: Surface Free Energy and Specific SurfaceArea

[0165] The fundamental quantity of inverse gas chromatography is the netretention volume, V_(N), determined from the retention time of a givensolvent. Adsorption of the probe molecules on solid surfaces-can beconsidered in terms of both dispersive and specific components ofsurface free energy, corresponding to non-polar and polar properties ofthe surface. By virtue of their chemical nature, non-polar probes of thealkane series only have dispersive component of surface free energy,which can be determined from the slope of the plot based the followingequation:

RTlnV _(N)=2aN _(A)(γ_(S) ^(D))^(1/2)(γ_(L) ^(D))^(1/2) +const

[0166] where R is the gas constant. T is the column's absolutetemperature, a is the probe's surface area. N_(A) is the Avogadro'snumber, γ_(S) ^(D) is the dispersive component of surface free energy ofa SX powder and γ_(L) ^(D) is the dispersive component of surface freeenergy of the solvent probes. Polar probes have both dispersive andspecific components of surface free energy of adsorption. The specificcomponent of surface free energy of adsorption (ΔG_(A) ^(SP)) can beestimated from the vertical distance between the alkane reference lineand the polar probes of interest. This free energy term can be relatedto the donor number (DN) and acceptor number (AN*) of the polar solventby the following equation: Δ  G_(A)^(SP) = K_(A)DN + K_(D)AN^(*)

[0167] DN describes the basicity or electron donor ability of a probewhilst AN* defines the acidity or electron acceptor ability. Here, AN*denotes a correction for the contribution of the dispersive componentand the entropy contribution into the surface energy is assumednegligible. Thus plotting—ΔG_(A) ^(SP)/AN* versus DN/AN* yields astraight line where K_(A) and K_(D) correspond to the slope andintercept respectively.

[0168] The IGC data for the various SX samples analysed by the aboveapproach are summarized in Tables 3 and 4. Comparison between differentmaterials shows that the magnitude of γ_(s) ^(D) is 15% smaller for S-SXcompounds than for both M-SX and G-SX compounds. In addition, ΔG_(A)^(SP) for all polar probes used reduced by at least half for S-SXcompound compared to the other two materials. Comparison between M-SXand G-SX materials indicates that, although the γ_(s) ^(D) are almostequal within the experimental error, ΔG_(A) ^(SP) for all the polarprobes is larger for the granulated material. The specific surface area,a, is twice as small for the S-SX compound compared with both M-SX andG-SX materials indicating that the mean surface-equivalent particlediameter for these compounds is smaller than for S-SX compound.

[0169] The reduced magnitude of γ_(s) ^(D) for S-SX compound impliesthat the surfaces of these panicles are less energetic for non-polar,dispersive surface interactions than the other two compounds. Theoverall strength of the polar interactions ΔG_(A) ^(SP) is also thesmallest for S-SX compound. Comparison between the K_(A) and K_(D)values of the three samples indicate that the acidity constant has thefollowing trend: K_(A)(S-SX)<K_(A)(M-SX)<K_(A)(G-SX). The basicityconstants follows the reverse order with K_(D)(S-SX) being the largest.Thus S-SX sample which has the weakest acidic property exhibits thestrongest basic interactions with respect to its exposed polar groups atthe interface. This suggests that S-SX crystal surfaces have, inrelative terms, more exposed basic groups but fewer exposed acidicgroups than both G-SX and M-SX compounds. Particles of all threecompounds have a similar platelet shape with the dominant {101} crystalfaces. However, S-SX particles have the largest shape factor, f (seeTable 3), which means that platelets of G-SX and M-SX are thicker. Theother materials have more energetic lateral crystal surfaces as a resultof the solution crystallisation procedure (G-SX) and particle breakageon micronisation (M-SX). Therefore the observed differences in K_(A) andK_(D), combined with the smallest magnitude of ΔG_(A) ^(SP) and γ_(s)^(D) for S-SX compound, suggests a combination of three differentfactors affecting the specific surface energy: (a) difference in thecrystal habit. i.e. the {001} crystal faces have stronger basic andweaker acidic interactions than the lateral crystal faces, (b) smalleroverall specific surface energy of the {001} crystal planes as comparedto any other crystallographic planes and (c) disturbances of the crystalstructure which also contribute to the higher surface energy of G-SX andM -SX compounds.

[0170] It is clear that solvent adsorption- progress more rapidly withthe M-SX and G-SX samples than with S-SX material. This fact indicatesthat supercritical fluid process of the invention produces particleswith lower surface activity (and greater surface stability) than powdersproduced by solution crystallisation and micronisation. TABLE 3 Compoundγ_(s) ^(D) (mJ/m²) K_(A) K_(D) S_(V) ƒ S-SX 32.476 0.110 0.356  7.0403.78 M-SX 38.285 0.172 0.298  9.243 2.80 G-SX 36.972 0.233 0.157 10.699—

[0171] TABLE 4 −ΔG_(A) ^(SP) (kJ/mol) Ethyl Diethyl DichloromethaneChloroform Acetone acetate ether tetrahydrofuran S-SX 2.808 0.153 3.7972.705 1.488 2.446 M-SX — 0.810 4.560 3.995 2.774 3.609 G-SX — 1.8855.454 4.739 2.958 4.854

[0172] Electrostatic Charge and Adhesion

[0173] Table 5 presents results on the charge, Q, and fraction ofadhered material, AD. S-SX particles exhibited significantly less(between one and two orders of magnitude) accumulated charge than themicronised powder before and after turbula mixing and also for thenon-adhered drug in cyclone separator. Correspondingly, the fraction ofadhered material is several times smaller for S-SX powder than for M-SXpowder in both the turbula mixing and cyclone separator tests.

[0174] These results are consistent with the superior powder flowproperties of S-SX material. Although the bulk powder density of S-SXmaterial is very low (about 0.1 g/cm³ vs. 0.5 g/cm³ for M-SX) it flowswell and does not adhere to the container walls. TABLE 5 Turbula MixerCyclone Separator Q (nCg⁻¹) Q (nCg⁻¹) AD Q (nCg⁻¹) Q (nCg⁻¹) AD BeforeAfter (% Before After (% mixing mixing w/w) mixing mixing w/w) S-SX−0.52 −0.17 1.5 4.9 −34.6 5.5 M-SX −12.1 −42.6 27 −48.4 −49.7 16.7

[0175] Particle Size and Powder Dispersability

[0176] The difference in PSD of S-SX and M-SX powders is reflected inthe magnitude of the mean particle sizes d_(4,3)=3.5 μm (S-SX) and 1.8μm (M-SX) and as measured using the LD technique. For both materials thecumulative PSD>98% within respirable particle size range 0.5<x<10 μm.However, a significant difference was observed between the dispersionbehavior of micronised and supercritically-processed powders. At highdispersing pressures above ≈2 bar, d_(4,3) is smaller for M-SX powder,as indicated by the primary PSD for this compound. This situationchanges dramatically at dispersing pressures below 2 bar. At lowpressures, S-SX powders consistently produce a large fraction of primaryparticles in the respiratory size range, whereas M-SX powders formstable agglomerates outside the 5 μm range which cannot be dispersed atsuch pressures.

[0177] The enhanced dispersability of S-SX powders-means a decrease ofthe inter-particulate contact area and/or reduction of the cohesiveforces leading to better performance of S-SX compound in the inhalationdevices. Despite a larger geometric (and volume) diameter for S-SXparticles, the Andersen cascade impactor measurements indicated agreater than two-fold increase (from 25.15 to 57.80%) of FPF for S-SXpowder compared with FPF of M-SX powder.

Example 3

[0178] This example measured the surface charge and adhesiveness ofparticles of the drug salbutamol sulphate produced using a SEDS™ processas compared to that of both the unprocessed starting material and amicronised sample of the drug.

[0179] Surface charge was examined by placing weighed portions of thesamples in a Faraday well to measure their electrostatic charge.

[0180] A simple adhesion test was devised to examine the observationthat the ultra-fine powders prepared by the SEDS™ process exhibited lowadhesion to containers and vessel walls, and low adhesive interactionwith surfaces in general. In this test, a small quantity of powder wasweighed into a screw topped glass jar and the jar rotated for 5 minutes.The non-adhering powder was then tipped from the jar and weighed and thepercentage powder adhering to the walls of the jar calculated.

[0181] The results of both the charge and the adhesion tests are shownin Table 6 below. It can be seen that both the unprocessed and themicronised materials exhibited relatively high surface charge, whilstthe figure for the SEDS™ sample was dramatically reduced. Further, inthe adhesion tests, there was minimal adhesion of the SEDS™-processedmaterial, whilst significant amounts of the micronised form of the samematerial adhered to the surfaces of the jar.

[0182] These findings are consistent with the surprisingly observed easyflowing nature of SEDS™ products, being different from the generallyobserved highly charged, cohesive and non-free flowing nature ofmicronised materials of a similar particle size. TABLE 6 Relative PowderAdhesion Sample Electrostatic Charge (nC/g) (to container walls)Unprocessed −23.1 8.6 Micronised −42.6 18.6 SEDS −0.2 1.0

Example 4

[0183] This example measured the specific surface area (by lowtemperature physical adsorption of nitrogen) of a poorly aqueous solubledrug produced using a SEDS™ process, as compared to a micronised sampleof the same drug.

[0184] The specific surface area of the micronised sample was 5.6 m²/g,whereas that of the SEDS™ sample was 27.8 m²/g.

Example 5

[0185] These examples assessed the dissolution performance of an aqueoussoluble compound produced using a SEDS™ process and also in a micronisedform. A conventional test method was used, as described in the currentpharmacopoeia and compendia (eg, BP and USP). Three SEDS™-producedsamples were tested.

[0186] The results are shown in FIG. 1, which plots the percentagedissolution against time. The ultra-fine particulate products of theinvention clearly dissolves much more rapidly and efficiently than themicronised version of the same substance, exhibiting much fasterdissolution profiles to complete dissolution. A further advantage of theSEDS™ products is the consistency of their dissolution profiles betweenrepeat batches.

Examples 6

[0187] These examples assessed the surface roughness of a SEDS™-producedmaterial as compared to that of (a) the crystallised starting materialand (b) the same compound in a micronised form. Conventional AFManalysis was used for the assessments.

[0188] The results are shown in FIGS. 2 (AFM analysis of theSEDS™-processed material) and 3 (graph showing RMS surface roughnessdata for the three samples) below. The SEDS™ sample clearly had asmoother topographical character.

Example 7

[0189] The properties of a micronised sample of salbutamol sulphate werecompared with those of a SEDS™-processed sample of the same drug. TheSEDS™ sample was prepared from a 10% w/v solution of salbutamol sulphatein acetone, using a 568 ml particle formation vessel, a two-passageconcentric nozzle with a 0.1 mm internal diameter orifice, a processingtemperature of 50° C. and pressure of 150 bar, a drug solution flow rateof 0.04 ml/min and a supercritical carbon dioxide anti-solvent flowingat 18 ml/min.

[0190] The mean amorphous content of the micronised sample, determinedby the dynamic moisture sorption method, was 6.92%, w/w (standarddeviation 1.10). That of the SEDS™ sample in contrast was only 0.13% w/w(SD 0.05).

[0191] The mean value for γ_(s) ^(D) (the dispersive component ofsurface free energy, determined by IGC) was 58.57 mJm⁻² (SD 2.19) forthe micronised sample but only 38.45 mJm⁻² (SD 1.50) for the SEDS™sample.

[0192] The mean specific charge of both samples was +4.00 nCg⁻¹ beforemixing. After triboelectrification by Turbula™ mixing this value hadincreased to +25.9 nCg⁻¹ for the micronised sample but only +16.4 nCg⁻¹for the SEDS™-produced sample.

[0193] Further, blends of salbutamol sulphate with lactose (both amicronised and a SEDS™-produced sample) were tested in an Andersen-typecascade impactor with a Clickhaler™ DPI device. The fine particlefraction of the emitted dose was measured as 11.86% for the micronisedsample and 33.57% for the SEDS™ one.

Example 8

[0194] The respiratory drug terbutaline suplphate (TBS) was prepared bySEDS™ process and its properties and DPI performance compared to thoseof a micronised sample of the same drug. The DPI performance of blendsof TBS with the carrier alpha-lactose monohydrate was also investigated,since the drug-carrier adhesion and hence the particulate (especiallysurface) properties of the drug and carrier, can significantly influencetheir dispersibilty in DPI systems.

[0195] Production of Powers

[0196] Materials

[0197] The material studied was supplied as micronised powder ofterbutaline sulphate (AstraZeneca R & D, Lund, Sweden), α-lactosemonohydrate (Pharmatose 325 M inhalation grade DMV International,Veghel, The Netherlands) was used as a carrier for the cascade impactionstudies. Carbon dioxide (BOC Ltd, UK) was 99.9% pure and methanol,ethanol and water were of HPLC grade (Fischer Scientific Limited,Loughborough, UK). Chloroform, toluene, ethyl acetate, acetone and1,4-dioxane, of HPLC grade (99+% purity) were used as polar probeswhereas a series of n-alkanes from hexane (n=6) to decane (n=10) of HPLCgrade (99+% purity) were used as non-polar probes for IGC analysis.

[0198] Solution Enhanced Dispersion by Supercritical Fluids (SEDS™)Process

[0199] For experiments that used ethanol as a solvent, the SEDS™ processwas modified in such a way that an additional extraction vessel packedwith TBS powder was placed in an oven and pure ethanol was pumpedthrough the vessel. This enhanced extraction of TBS and resulted inproduct yield >85% w/w (see FIG. 4, vessel position indicated by dottedlines). All other experiments were conducted in a SEDS™ apparatus asdisclosed in WO 95/01221 consisting of a stainless steel particleformation vessel (50 ml) positioned in an air assisted heated oven witha specially designed two flow coaxial nozzle capable of withstanding apressure of 500 bar. Pressure in the system was maintained within ±1 barby an automated back-pressure regulator (Tescom, Japan). Drug solution(2% w/v) was delivered by a separate reciprocating HPLC pump (JascoPU-980, Japan) and varied between 0.1 and 4.8 ml/min. Liquid CO₂ (−10°C.) was pumped by a water-cooled Dosapro Milton Roy pump (Type: MB 112S(L) 10M 480/J VV2, Pont-Saint-Pierre, France) and flow was variedbetween 4.5 and 80 ml/min. The CO₂ passed through a heat exchanger toensure that it was supercritical before entering the nozzle, whichconsisted of two concentric tubes and a small premixing chamber. Twonozzle diameters, 0.1 and 0.2 mm were used in the study. The powder(typically about 200 mg a batch) was collected from the vessel andanalysed. A range of operating temperatures (35-80° C.) and pressures(80-250 bar) were applied to produce drug powder using the SEDS™process.

[0200] Physical Characterisation of Powders

[0201] Particle Size Analysis

[0202] Laser Diffraction

[0203] A small amount of TBS powder was analysed using a laserdiffraction RODOS/VIBRI dispersing system (HELOS/RODOS, Sympatec GmbH,Clausthal-Zellerfeld, Germany). The instrument consisted of a lasersensor HELOS and a RODOS dry-powder air-dispersion system (SympatecGmbH, Clausthal-Zellerfeld, Germany). Different measurement ranges ofthe laser sensor were provided by interchangeable objectives R1 (0.1-35μm) and R2 (0.25-87.5 μm). The rate of powder dispersion was controlledby adjusting the pressure of the compressed air flow. A pressure of 2bar was sufficient to achieve deagglomeration of primary particleswithout attrition.

[0204] Time-of-Flight Measurements

[0205] The TBS samples were also analysed using an AeroSizer™ (AmherstProcess Instruments, Amherst, Mass., USA), provided with pulse jetdisperser, the AeroDisperser™, to introduce the powders to theinstrument. The measurement range of the AeroSizer™ is nominally from0.2 to 200 μm of aerodynamic diameter with the standard 750 μm diametertapered nozzle. The micronised and SEDS™ TBS samples were analysed for300 seconds in triplicate using normal deagglomeration conditions, feedrate (5000 particles per second ) and medium shear force (0.5 psi).

[0206] Scanning Electron Microscopy (SEM)

[0207] A small amount of powder was manually dispersed onto a carbon tabadhered to an aluminium stub, (Agar Scientific, UK). The sample stubswere coated with a thin layer (200 Å) of gold by employing an EmitechK550 sputter coater (Texas, USA). The samples were examined by SEM(Hitachi S-520, Tokyo, Japan) and photographed under variousmagnifications with direct data capture of the images onto a personalcomputer.

[0208] Solid State Analysis

[0209] X-Ray Powder Diffraction (XRPD)

[0210] Structural analysis of the samples was performed using an X-raypowder diffractometer (Siemens, D5000, Karlsruhe, Germany), fitted witha rotating sample holder, a scintillation counter detector and adivergent beam utilising a CuKα source of X-rays (λ=1.5418 Å). Eachsample was placed in the cavity of an aluminium sample holder flattenedwith a glass slide to present a good surface texture and inserted intothe sample holder. In order to measure the powder pattern, the sampleholder and detector were moved in a circular path to determine theangles of scattered radiation and to reduce preferred sampleorientation. All samples were measured in the 2θ angle range between1.5° and 45° with a scan rate of 3 seconds/step and a step size of0.05°. Samples were analysed in duplicate.

[0211] Differential Scanning Calorimetry (DSC)

[0212] Prior to sample analysis, a baseline was obtained which was usedas a background. DSC analyses of terbutaline sulphate samples werecarried out on a Perkin Elmer 7 Series differential scanning calorimeterthermal analysis system (Perkin Elmer Ltd., Beaconsfield, UK).Temperature and enthalpy were calibrated with the standard materialsindium (melting point=156.6° C.) and zinc (melting point=419.5° C).Samples (1-10 mg) were accurately weighed into pierced, crimpedaluminium pans and heated at 10° C. min⁻¹ over a heating range of25-290° C. under a nitrogen purge. A chiller unit was used inconjunction with the calorimeter to attain the lower temperatures.

[0213] Dynamic Vapour Sorption (DVS)

[0214] The moisture sorption isotherm of each powder at 25° C. wasmeasured using a dynamic vapour sorption (DVS) instrument made bySurface Measurement Systems, UK. This instrument gravimetricallymeasures uptake and loss of water vapour on a substrate by means of arecording microbalance with a resolution of ±0.1 μg. In the first stepof the experimental run, the sample was dried at 25° C. and 0% relativehumidity (RH) for at least 600 minutes to bring the sample to near zerowt % H₂O. Then, the instrument was programmed to increase the RH insteps of 5% RH from 0% to 90% RH and decrease the RH in steps of 10% RHfrom 90% to 0% RH. A criterion of dm/dt=0.005%/min was chosen for thesystem to hold at each RH step before proceeding to the next RH step.Sample masses between 30 and 100 mg were used in this study. The changein mass (%) is expressed in terms of g H₂O per 100 g of dry substance.

[0215] Isothermal Microcalorinietry

[0216] A Thermal Activity Monitor (TAM, model 2277; Thermometric A B,Järfälla, Sweden) was used to measure the calorimetric heat flow (μW)vs. % RH profile of each sample. A RH-perfusion cell (Model 2255-120)accessory for the TAM was used to control RH within the sample vessel.The carrier gas, dry N₂, was flowed at a constant rate (1.48cm^(3/)min). All experiments were performed at 25° C. About 100 to 105mg accurately weighed of each powder were placed in a stainless steelampoule, attached to the RH perfusion cell, and then dried under 0% RHuntil a stable heat flow signal was reached (e.g., a signal within therange of −1 to +1 μW). The RH was then increased in a linear ramp from 0to 90% over the following 30 hours (i.e., 3% RH/hr). The heat flowarising from interactions of water vapour with the solid sample wasmeasured as a function of time. Since RH changed with time in a linearfashion, the heat flow was also known as a function of RH.

[0217] The TAM measures the total heat flow in power, P, produced fromeither a physical or chemical reaction. In this study the calorimetricpower is proportional to the rate of moisture sorption or desorption,crystallization, and/or other processes. Exothermic events are measuredas a deflection in the positive y-axis direction. Althoughcrystallization is an exothermic process, it can be observed as a netendothermic process. During crystallization, there is an exotherm due tocrystallization and a simultaneous endotherm due to desorption ofpreviously sorbed moisture. The TAM profile gives the resultant of theseprocesses. Hence, for crystallization, the TAM profile can be anexothermic peak only, an endothermic peak only or a sequentialcombination of both exothermic and endothermic peaks.

[0218] Inverse Gas Chromatography (IGC)

[0219] An empty GC column was uniformly packed with the powder ofinterest (TBS). Pre-silanised commercially available straight glasscolumns of 30 cm length with a 3 mm internal diameter were used in thisinvestigation. The silanation procedure was necessary to minimize activesites on the inner glass surfaces, which strongly interact with polarprobes. Each column was packed at the detector end with a small amountof silanised glass wool, was clipped to a stand and powder was addedthrough a glass funnel with the aid of a mechanical column packer(tapping) to improve powder flow and remove any air gaps. Once thecolumn had been filled, the injector end of the column was also packedwith silanised glass wool and attached to a separate, purpose builtcolumn oven that controls the sample (column) temperature between roomtemperature and 90° C. A. Hewlett Packard 6890 Series Gas Chromatograph(GC) (Hewlett Packard, Penna, USA) oven equipped with an autosampler wasused to control the solvent temperature. The 6890 GC data acquisitionsystem was used to record data from a thermal conductivity detector(TCD) and flame ionisation detector (FID) with the instrument modifiedfor IGC by Surface Measurement Systems (SMS), Manchester, UK. Thecombination of detectors allowed sensitive analysis of both organicvapour elution and water (although RH was not raised above 0% for theseexperiments).

[0220] The whole system was fully automated by control software (SMS iGCController v1.3) and the data analysed using SMS iGC Analysis macros.Prior to analysis, each column was equilibrated at 30° C. and 0%relative humidity (RH) for 5 hours by passing dry helium gas through thecolumn. Helium gas was also used as the carrier gas. Hydrogen andcompressed air flow rates were set at 40 and 450 ml min⁻¹ respectivelyfor the FID. The chromatograph injection port was maintained at 80° C.,TCD detector at 150° C. and the FID detector at 150° C. Columntemperature was set at 30° C. throughout analysis. Data were obtained byflowing helium gas at 10 ml min⁻¹ through the sinalised glass columnpacked with a known weight of powdered material and injecting smallamounts (concentration P/Po=0.05) of a range of probe vapours withdifferent polarities. The retention times of the probes were measuredusing SMS iGC Controller v1.3 software, at infinite dilution or nearzero surface coverage (equivalent to 10⁻⁴−10⁻⁷ μl of liquid) whereretention is independent of the quantity of probe injected. For eachsample, two columns were prepared and analysed by employing a methodbased on standard settings, which allows the precise control andmeasurement of experimental variables. This is essential in producingmeaningful results. The data were used to calculate the dispersive andnon-dispersive forces acting at TBS particle surfaces using the methoddeveloped by Schultz and co-workers (J. Schultz, L. Lavielle and C.Martin. The role of the interface in carbon fibre-epoxy composites, J.Adhesion, 23, 45-60 (1987)).

[0221] Powder Analysis

[0222] Aeroflow Method

[0223] An Aeroflow™ powder avalanching apparatus (Amherst ProcessInstruments, API, Amherst, USA) was employed to analyse the dynamicavalanching behaviour of micronised and SC processed TBS samples. TheAeroflow apparatus consists of a transparent rotating drum with a portat the front. A white light source is positioned in front of the drumand a masked array of photocells is behind the drum. To measureavalanching, 50ml of the drug powder was added to the drum, which isabout 15% of its total volume to ensure good powder mixing during theoperation. As the drum rotates, the powder bed is carried upwards untilan unstable state is reached and an avalanche occurs.

[0224] The time between successive avalanches was recorded by theprojection of the light beam through the drum onto the photocell array.The photocells generated a voltage dependent on the amount of lightfalling on the cells and the area of unmasked photocells shielded fromthe light source by the powder. The voltage output (transmitted lightintensity) was recorded by a computer, which translates the output aspowder movement using a technique disclosed in B. H. Kaye.Characterising the flowability of a powder using the concepts of fractalgeometry and chaos theory, Part. Part. Charact. 14: 53-66 (1997). EachTBS sample was tested in duplicate and mean avalanche time andirregularity (scatter) of avalanches were recorded.

[0225] Powder Dispersion by Cascade Impaction

[0226] An Andersen Cascade Impactor (1 ACFM Eight Stage Non ViableAndersen Cascade Impactor, Copley Ltd, Nottingham, UK) was used todetermine the dispersability and fine particle fraction (FPF) of eachpowder/carrier blend and pure drug alone through a dry powder inhalerdevice (Clickhaler®, Innovata Biomed, St. Albans, UK). To preventparticles from bouncing off the plates and becoming re-entrained in theair stream prior to each analysis, the eight metal plates of theimpactor were coated with a thin layer of silicone spray and left to dryfor 30 minutes. A pre-separator was attached to the top of the impactorto prevent large particles or aggregates from reaching the stages. Theair flow through the apparatus, measured at the inlet to the throat, wasadjusted to generate a pressure drop of 4 kPa over the inhaler undertest and a duration consistent with the flow of 4 litres min⁻¹ accordingto compendial guidelines (Pharm Forum, 22: 3049-3095 (1996). Theseconditions are consistent with a flow rate of 49 1 min⁻¹ and 4.9 sduration. A blend containing 3.8% w/w of compound, hand-filled into thereservoir of a Clickhaler® device, which is capable of delivering 200 μgof drug per actuation, was used. Ten doses were discharged into theapparatus and each determination was carried out at least twice. Aftereach determination, the powder on each impaction stage was collected byrinsing with mobile phase and the resulting solutions were analysed byHPLC. The amount of drug deposited in the throat piece and thepre-separator was also determined.

[0227] The Andersen cascade impactor is traditionally calibrated at 28.31 min⁻¹ but may be operated at higher flow rates, which are thought tomore closely approximate a patient's capabilities (F. Podczeck.Optimisation of the operation conditions of an Andersen-Cascade impactorand the relationship to centrifugal adhesion measurements to aid thedevelopment of dry powder inhalations, Int. J. Pharm., 149: 51-61(1997)). Using a variation of the Stokes' equation, effective cut-offdiameters (ECDs) at the higher flow rate can be calculated from theequation given below (M. M. Van Oort, B. Downey, and W. Roberts.Verification of operating the Andersen Cascade Impactor at differentflow rates, Pharm. Forum, 22: 2211-2215 (1996).

ECD _(F2) =ECD _(28.3)(28.3/F2)^(1/2)

[0228] where ECD_(F2) is the ECD at the alternative flow rate,ECD_(28.3) is the manufacturer's flow rate (28.3 1 min⁻¹) and F2 is thealternative flow rate in 1 min⁻¹. The alternative flow rate used in thisstudy was 49 1 min⁻¹. Particles collected on the filter were smallerthan 0.32 μm. The percentage of the total dose collected on the stages 1through 5 represented particles with the aerodynamic diameters less than4.36 μm, and was considered as the fine particle fraction (FPF).

[0229] Results and Discussion

[0230] Powder Preparation and Optimisation

[0231] TBS was produced using the SEDS™ process. Different solvents suchas pure methanol, methanol/water, pure water and pure ethanol were usedto dissolve drug material between 1-10% w/v in concentration. Tooptimise the particle properties (crystallinity, shape, size, sizedistribution) a number of parameters such as concentration of the drug,drug solution flow rate, CO₂ flow rate, temperature and pressure of thesystem were manipulated. A wide range of SEDS™ products such as ahydrated crystal, amorphous material, and two previously reportedpolymorphs A and B were produced using different solvents andexperimental conditions, as seen in FIGS. 5a-f. For example, the cleardifference in morphology and crystallinity (determined by XRPD which wasbased on diffraction peaks area and DSC by measuring change in enthalpyof fusion) of TBS1 (127.12 J/g) and TBS2 (88.68 J/g) may be attributedprimarily to the different residence time for particle formation andmixing in vessels which is defined as τ=V/f, where V is the volume ofthe vessel and f is the volumetric flow rates of ethanol and CO₂ atgiven temperature and pressure respectively. Particles in the smaller 50ml vessel were exposed to partially mixed ethanol-rich phase which existin the core of high velocity jet (B. Y. Shekunov, J. Baldyga, and P.York. Particle formation by mixing with supercritical antisolvent athigh Reynolds numbers, Chem. Eng. Sci., 56: 2421-2433 (2001)), whereasthe particles in the large 500 ml vessel were accumulated in well mixedCO₂ -rich phase.

[0232] SEM photomicrographs of a typical micronised and SCF processedbatches of TBS are shown in FIGS. 5a-f. The use of different solventssuch as pure methanol and methanol/water resulted in needle-like as wellas-spherical amorphous particles respectively. Particles obtained usingpure methanol, pure ethanol and pure water have revealed well-definedcrystal edges compared to micronised particles.

[0233] Particle Size

[0234] The average particle size by volume determined by laserdiffraction for a typical batch of TBS1 and TBS2 was between 3.2 and 3.4μm with 90% less than 7 μm in comparison to 3.0 μm microparticles ofmicronised terbutaline sulphate with 90% less than 5 μm. This methodshowed good reproducibility and therefore, was used for the qualitycontrol assessment.

[0235] The samples were also analysed with the AeroSizer™. Micronised,TBS1 and TBS2 samples have similar aerodynamic diameters to thoseobtained by the Sympatec™ laser diffraction instrument. However, TBS3,TBS4 and TBS5 showed larger mean diameters by AeroSizer™ in comparisonto laser diffraction analysis. These results are depicted in Table 7below. The AeroSizer™ gives an aerodynamic equivalent diameter, which issmaller than geometric volume diameter for non-spherical primaryparticles. Therefore, the results here likely indicate insufficientdispersion by AeroDisperser™ of the agglomerated particles of bothbatches TBS4 and TBS5 (FIG. 5e,f). In addition, the sampling proceduresin the AeroSizer™ nozzle may produce discrepancies in time-of-flightmeasurements at large particle number densities, which is the case ofsmall amorphous particles in FIG. 5e. Therefore, the reproducibility ofresults for this technique was lower than for the laser diffractionmethod. TABLE 7 Sympatec Aerosizer Sample D_(4,3) (μm) D_(4,3) (μm)Micronised 3.04 2.69 TBS 1 3.22 3.31 TBS 2 3.43 3.44 TBS 3 1.99 6.69 TBS4 4.75 15.53  TBS 5 4.84 11.44 

[0236] X-Ray Diffraction and DSC Profiles

[0237] The X-ray powder patterns in FIGS. 6a-c illustrate thecrystallinity of micronised and TBS1 and TBS2 samples, which is assessedon the basis of the sharpness of the major diffraction peaks. From theresults it can be seen that there is no significant difference in theXRPD profiles of micronised and TBS1 samples. However, based on XRPDdata, the TBS2 sample has shown lower bulk crystallinity in comparisonto the micronised sample. The DSC profiles (Table 8) confirm thisconclusion; the fusion enthalpy for TBS2 batch is considerably lowerthan for both micronised and TBS1 batches, thus the crystallinity forTBS1 being higher than that for the micronised material. TABLE 8 MeltingPoint Enthalpy of Fusion Sample (° C.) (J/g) Identification Micronised266.3 121.76 Form B TBS 1 267.1 127.12 Form B TBS 2 266.3 88.68 Form BTBS 3 266.3 31.35 Amorphous TBS 4 274.5 40.98 Hydrate TBS 5 272.7 57.69Form A

[0238] Interactions of Water with Micronised and SEDS™ Powders

[0239] The sorption and desorption isotherms of micronised and SCprocessed TBS show that at 25° C., the equilibrium moisture content(“moisture uptake”) of all TBS samples in this study is very low (<0.4%)at any RH value. The low moisture uptake indicates that each powder iscrystalline. However, TBS2 sample showed slightly higher moisture uptakethan the micronised sample, which is consistent with its lower bulkcrystallinity indicated by DSC and X-ray diffraction (see FIG. 6 andTable 8). Typically, an amorphous or partially crystalline material willtake up more moisture than a highly crystalline material. TBS2 alsotakes up more moisture at relative humidities beyond 90% RH. Under theseconditions, the sample may be deliquescing at high RH.

[0240] In FIG. 7, the heat flow (μW) for both micronised and SEDS™powders of TBS are normalised to 1 mg for comparison. The endothermicpeak for micronised TBS is most likely due to crystallisation of theamorphous fraction that was previously induced by micronisation. The TAMprofile for TBS2 sample of TBS has an incomplete exothermic peak between85 and 90% RH because the RH ramping experiment (3% RH/hr from 0% to 90%RH) ended before the event was completed. No exothermic or endothermicpeaks were observed in the TAM profile of TBS1 sample of TBS, which istypical for a highly crystalline material. The TAM results show that themicronised TBS has an event at about 79% RH, probably due tocrystallisation. The results also show that TBS2 sample has anexothermic event at about 85% RH.

[0241] Surface Energetics Properties

[0242] Micronised and supercritically processed TBS1 materials show verysimilar surface energetics with marginally lower non-polar, dispersivesurface interaction (γ_(s) ^(d)) and slightly higher specificinteraction (−ΔG_(A) ^(SP)) for polar, amphoteric and basic probes. Incontrast, the TBS2 sample indicated significantly less energetic, bothdispersive and specific, interactions (Table 9). In addition, comparisonof the K_(A) and K_(D) values of TBS2 and micronised samples (Table 10)indicates the weakest, both acidic and basic interactions for thissupercritically processed material. Thus, the SEDS™ material has lessexposed energetic acidic and basic groups. This also indicates that thesurface of TBS2 particles may have a more ordered structure than thatfor micronised material, despite the fact that the bulk structuredetermined using X-ray diffraction and DSC techniques appeared moreordered for the micronised particles. Micronised material is sometimesconditioned before being used for a DPI formulation, by passing asaturated ethanol vapour through the powder bed. Similarly, TBS1material was produced with an excess of ethanol solvent. Therefore, itis possible that the surface structure was modified after particleformation for micronised and TBS1 materials and disorganised compared tothe crystal structure in the bulk. TABLE 9 −ΔG_(A) ^(SP) (kJ/mol) Ace-Ethyl Chloro- Sample γ_(s) ^(D) mJ/m⁻² Tolune tone acetate form DioxaneMicronised 58.61 3.42 12.57 16.01 1.79 15.96 TBS 1 57.37 3.66 13.4116.65 1.68 — TBS 2 55.05 2.85 10.42 13.76 1.21 14.20

[0243] TABLE 10 Sample K_(A) K_(D) Micronised 0.892 0.051 TBS 1 0.7610.020 TBS 2 0.778 0.032

[0244] Powder Flow Properties

[0245] For data obtained using the Aeroflow™ powder avalanchinganalyser, interval times between avalanches were plotted as discretephase maps known as strange attractor plots (B. H. Kaye, J.Gratton-Liimatainen, and N. Faddis. Studying the avalanching behaviourof a powder in a rotating disc, Part. Part. Charact. 12:197-201(1995).Free-flowing powders produce strange attractor plots close to the originwith small spread, whilst, in contrast, cohesive powders give plots witha larger spread and a centroid positioned further from the origin. Thestrange attractor plots for TBS analysed at high (100 seconds perrevolution) and medium (145 seconds per revolution) rotation speed areshown in FIG. 8 and FIG. 9, respectively.

[0246] Examination of the strange attractor plots provides a clear,visual display of the difference in flow behaviour between themicronised and TBS2. The SEDS™ sample has a lower irregularity and alower mean avalanche time (see Table 11 and FIGS. 8 and 9) compared tomicronised TBS. Therefore, micronised TBS exhibits poorer flow behaviourthan TBS2 material. Since a relatively large quantity (≈10 g) of powderis required to perform powder flow behaviour study, no comparison wasmade between TBS1 and micronised samples. TABLE 11 Mean time toIrregularity of Sample avalanche (s) flow (s) Micronised (100 sec/rev)3.62 1.28 Micronised (145 sec/rev) 5.72 2.39 TBS 2 (100 sec/rev) 3.301.17 TBS 2 (145 sec/rev) 4.91 2.12

[0247] Enhanced flow properties of TBS2 sample are consistent with lowerenergetics and lower cohesiveness of this material as indicated by theIGC measurements and the following ACI studies.

[0248] Aerosol Performance of Micronised vs SEDS™ Powders

[0249]FIGS. 10 and 11 compare the in vitro performance of micronised andSEDS™ processed TBS analysed in a lactose blend as well as pure drugalone. The ACI measurements demonstrated that the TBS2 batch in bothcases produced a significantly higher FPF in comparison to bothmicronised and TBS1 material. For this material, a high proportion offine particle mass with a narrow distribution was collected on stage 1-3in contrast to the broad distribution across stages 1-5 for themicronised material. The SC processed TBS2 material also demonstrated anincreased fine particle fraction (FPF) in both lactose blend and drugalone compared to micronised powders (38.6% vs 30.7%, and 29.6% vs17.7%) and increased emitted dose (see Table 12). Since the lactoseparticles are large and cannot penetrate beyond the pre-separator stage,this indicates that dispersion between pure drug particles and formationof loose aggregates plays a major role in defining the depositionprofile. TABLE 12 Total Emitted Dose Fine Particle Fraction (μg/dose)(%) Drug and Lactose Drug Drug and Lactose Drug Sample Blend Alone BlendAlone Micronised 80.6 84.2 30.7 17.7 TBS 1 71.6 83.7 11.4 9.4 TBS 2104.8 98.8 38.6 29.6

[0250] The main factor responsible for better performance ofsupercritically processed TBS powder in the ACI is possibly related tothe dispersibility of this powder at low air flow rates. The enhanceddispersibility is particularly significant for DPI devices where theperformance strongly depends on powder deaggregation at relatively lowdispersion forces. Clearly, high turbulence is favourable for dispersionbut it inevitably leads to high pressure differentials which may beunacceptable for correct functioning of many devices.

Example 10

[0251] The example assessed the force of adhesion of particles ofsalbutamol sulphate produced using a SEDS™ processes compared to thesame compound in micronised form. Conventional AFM analysis was used.Particles of the samples were mounted onto AFM probes and the adhesionforce per unit area to a freshly cleaved highly oriented pyrolyticgraphite substrate (HOP G, Agar Scientific, Essex, UK) in a liquid (2H3H perfluoropentane) environment was determined. The contact areainvolved in the interaction was assessed and related to the forcemeasurements.

[0252] The initial forces for individual particles of the micronised andSEDS™ produced materials were 15.77 nN (SD 4.55 nN) and 4.21 nN (SD 0.71nN) respectively.

[0253] Following correction for surface area, the forces per unit areawere 100.91 nN/μm² (SD 29.15 nN/μm²) for the micronised material and13.52 nN/μm² (SD 2.27 nN/μm²) for the non-micronised SEDS™ processproduced material. The particulate product of the invention clearlydemonstrates lower adhesiveness than the micronised version of the samesubstance.

Example 11

[0254] The aerosol performance of a SEDS™ processed sample ofbromocriptine mesylate was assessed in a unit-dose passive inhalerdevice (Turbospin PH & T (Italy)), at a peak inspiratory flow rate(PFIR) of 28.3 LPM and 60 LPM. TABLE 13 Emitted dose performance withrelative standard deviations of SEDS bromocriptine using Turbospin.Errors correspond to RSDs. Fill Flow Weight Rate ED Left in Capsules(mg) (LPM) (%) (%) 8.0 28.3 67.7 ± 14.7 10.5 ± 118  60 87.5 ± 3.4  −0.1± −2320 4.0 28.3 75.4 ± 3.9  −1.5 ± −134  60 83.8 ± 4.0   0.5 ± 347 

[0255] The aerosol analysis (performed @ 60 LPM) indicated thatbromocriptine yielded aerosol particles within respirable range with anaerodynamic diameter of 4.2/μm (4.3% RSD) and an improved FPF (42% ofED).

[0256] Bromocriptine dispersed well at high flow rates (ED>80%)regardless of full weight. Moreover, it exhibited minimal flow ratedefendence, as ED drops were minimal (8-20%) following emptying of thecapsules.

1. An active substance in particulate form suitable for administrationvia a dry powder inhaler, said particulates comprising: a) a volume meanaerodynamic diameter of less than 7 microns; b) a density less than 0.5g/ml; and c) a surface-to-volume ratio of at least twice that ofspherical particles of the same volume diameter.
 2. An active substanceas in claim 1 wherein the surface-to-volume ratio is at least 2.5 timesthat of spherical particles of the same volume diameter.
 3. An activesubstance of claim 1 further comprising a shape factor of at least
 2. 4.An active substance of claim 1 further comprising a shape coefficient ofgreater than
 10. 5. An active substance of claim 1 further comprising anaerodynamic shape factor of at least 1.4.
 6. An active substance ofclaim 1 further comprising a specific surface area of at least 10 m²/g.7. An active substance of claim 1 further comprising a specific surfacearea of at least 15 m²/g.
 8. An active substance of claim 1 furthercomprising a specific surface area of at least 20 m²/g.
 9. An activesubstance of claim 1 further comprising a specific surface area of atleast 25 m^(2/)g.
 10. An active substance of claim 1 further comprisinga volume mean diameter of less than 6 microns.
 11. An active substanceof claim 1 further comprising a specific surface energy of less than 100mJ/m².
 12. An active substance of claim 1 further comprising a specificsurface energy of less than 70 mJ/m².
 13. An active substance of claim 1further comprising an aggregate tensile strength less than 0.8.
 14. Anactive substance of claim 1 further comprising a surface weighted domainsize of at least 400 Å.
 15. An active substance of claim 1 furthercomprising a volume weighted domain size of at least 700 Å.
 16. Anactive substance of claim 1 further comprising a total strain less than0.7×10⁻³.
 17. An active substance of claim 1 further comprising a meanspecific charge from −5 to +5 nCg⁻¹.
 18. An active substance of claim 1further comprising a RMS roughness, measured using AFM, of 0.5 nm orless.
 19. An active substance of claim 1 further comprising a dispersivecomponent of surface free energy, γ_(S) ^(D), which is at least 5% lowerthan for the corresponding active substance made by micronisation,granulation, or solvent crystallization.
 20. An active substance ofclaim 1 further comprising a specific component of free surface energyof absorption, ΔG_(A), which is at least 10% lower than for thecorresponding active substance made by micronisation, granulation, orsolvent crystallization.
 21. An active substance of claim 1 furthercomprising a mean adhesion fraction following triboelectrification in aturbula mixer which is 50% or less of that for the same active substancemade by micronisation, granulation, or solvent crystallization.
 22. Anactive substance of claim 1 further comprising a theoretical aggregatetensile strength, σ, which is no more than 0.8 times that for particlesof the same active substance made by a micronisation, granulation, orsolvent crystallization.
 23. An active substance of claim 1 furthercomprising a particle size distribution (X₉₀) of from 0.5 to 10 μm. 24.An active substance of claim 1 further comprising a particle sizespread, measured using a cascade impacted technique at low turbulence,which is at least 5% smaller and with a mean diameter which is at least10% smaller than that of the corresponding active substance made bymicronisation, granulation, or solvent crystallization.
 25. An activesubstance of claim 1 further comprising a total crystal strain, ε, whichis at least 30% lower than that for particles of the same activesubstance made by micronisation, granulation, or solventcrystallization.
 26. An active substance of claim 1 further comprisingan amorphous phase content which is at least 10 times lower than thatfor particles of the same active substance made by micronisation,granulation, or solvent crystallization.
 27. An active substance ofclaim 1 further comprising a mean specific charge followingtriboelecrification which is at least 50% lower than for thecorresponding active substance made by micronisation, granulation, orsolvent crystallization.
 28. An active substance of claim 1 furthercomprising a mean avalanche time as determined using a powderavalanching apparatus which is at least 5% lower at 100s/rev than forthe corresponding active substance made by micronisation, granulation,or solvent crystallization.
 29. An active substance of claim 1 furthercomprising a mean avalanche time as determined using a powderavalanching apparatus which is at least 10% lower at 145 s/rev than forthe corresponding active substance made by micronisation, granulation,or solvent crystallization.
 30. An active substance of claim 1 furthercomprising an amorphous phase content of less than 1% w/w.
 31. An activesubstance of claim 1 further comprising a bulk powder density of 0.2g/cm³ or less.
 32. An active substance of claim 1 further comprising ashape factor of at least 3.5.
 33. An active substance of claim 1 furthercomprising a RMS roughness, measured using atomic force microscopy, of0.2 nm or less.
 34. An active substance of claim 1 which when deliveredusing a passive dry powder inhaler yields a fine particle fraction inthe emitted dose of 20% or greater.
 35. An active substance according toclaim 34 which yields a fine particle fraction in the emitted dose of31% or greater.
 36. An active substance according to claim 34 whichyields a fine particle fraction in the emitted dose of 55% or greater.37. An active substance according to claim 1 comprising apharmaceutically or nutraceutically active substance.
 38. An activesubstance according to claim 37 wherein the active substance is apharmaceutically active substance or a mixture thereof.
 39. An activesubstance according to claim 38 wherein the active substance is selectedfrom the group consisting of salbutamol, terbutalene, salmeterol,fenoterol, bromocriptine or a pharmaceutically acceptable salt ormixture thereof.
 40. A method of administering an active substance byinhalation comprising providing a composition according to claim 1 andadministering said composition to the respiratory tract.
 41. A methodaccording to claim 40 wherein the composition is administered via apassive dry powder inhaler.
 42. An active substance in particulate formwhich when delivered using a passive dry powder inhaler yields a fineparticle fraction in the emitted dose which is at least 20% greater thanthat of the same active substance produced by micronisation,granulation, or solvent crystallization and having the same or smallervolume mean diameter.
 43. An active substance in particulate form whichwhen dispersed at a shear stress of between 5 and 30 Nm² gives a volumemean particle diameter at least 10% smaller than that for the sameactive substance made by micronisation, granulation, or solventcrystallization.